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HCPCS Level II A0431: Ambulance Service, Rotary-Wing Air Transport, One Way

HCPCS Level II code A0431 represents one-way rotary-wing air ambulance transport using conventional air services. This code captures rotary-wing conveyance of patients when rotary-wing transport is medically indicated or operationally required. Nationally, air ambulance services play a critical role in trauma systems, rural access, and interfacility transfers for time-sensitive conditions.

Key payers discussed in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of billing context for A0431, typical sites of service, and the clinical scenarios in which rotary-wing transport is used. The publication outlines benchmarking elements and policy considerations relevant to coverage and payment for air ambulance trips, summarizes common modifiers used in practice (input list provided), and identifies where input data are not available.

This briefing is focused on national implications: how A0431 is applied across payers, the operational settings for rotary-wing transports, and the key items stakeholders monitor — service definitions, payer policies, and coding clarity. Data not available in the input is noted where applicable. The reader will gain a clear, actionable understanding of what A0431 denotes and the primary issues that affect reimbursement and clinical deployment of rotary-wing air ambulance services.

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Billing Code Overview

HCPCS Level II code A0431 describes ambulance service, conventional air services, transport, one way (rotary wing). The service type is emergency or non-emergency rotary-wing air ambulance transport provided for a one-way transfer of a patient. The typical site of service is air transport between points not accessible or practical by ground ambulance, including interfacility transfers and scene responses requiring rotary-wing conveyance.

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HCPCS Level II A0431: Ambulance Service, Rotary-Wing Air Transport, One Way

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Billing Code Overview

Clinical & Coding Specifications

Clinical Context

A typical patient is a critically ill adult involved in a multi-vehicle crash with suspected internal hemorrhage and unstable vital signs requiring rapid en route advanced care and definitive hospital-based intervention. Emergency Medical Services on scene determine that ground transport would delay time-sensitive care; the patient is loaded into a rotary-wing air ambulance for one-way transport to a level I trauma center. Flight crew documents on-scene assessment, initiation of advanced airway management, intravenous access with blood product administration, continuous cardiac and hemodynamic monitoring, and radio/handoff to receiving trauma team. Billing uses A0431 for the one-way conventional rotary-wing transport; appropriate modifiers are appended to reflect circumstances (for example, medical necessity, bilateral services, hospital-based origin/destination, or unusual service complexity). Typical sites of service include landing zones adjacent to the scene, helipads at sending hospitals, and receiving hospital helipads or emergency departments. The clinical workflow includes scene triage, flight activation, in-flight critical care interventions, prearrival notification to the receiving facility, patient transfer to the receiving team, and completion of transport documentation required for billing and medical record continuity.

Coding Specifications

Modifier	Description	When to Use
`22`	Increased procedural service	Use when the rotary-wing transport required substantially greater resources or time than usual due to patient complexity (document rationale).
`23`	Unusual anesthesia	Use if the patient required general anesthesia provided by the flight team during transport (rare for air ambulance but applicable if anesthesia-level care provided).
`52`	Reduced services	Use when the transport was partially completed or services were reduced compared to full service.
`53`	Discontinued procedure	Use if the flight was aborted for medical or safety reasons after initiation.
`76`	Repeat procedure by same provider	Use if the same air ambulance provider performed a repeat one-way transport for the same patient on the same date.
`78`	Return to operating/procedure room	Use if the transport was immediately followed by return to surgery or interventional procedure and indicates relatedness to prior procedure.
`80`	Assistant surgeon	Not typically used with `A0431`; include only when billing combined services that require reporting of assistant involvement.
`82`	Assistant (when qualified resident not available)	Use in rare cases where an assistant surgeon qualifier is required alongside other procedural reporting.
`QK`	Medical direction of two to four concurrent anesthesia procedures	Use only if applicable for billed anesthesia services provided during transport and medical direction rules apply.
`QX`	CRNA service with medical direction by physician	Use when a CRNA provided anesthesia-level care during transport with physician supervision and attribution rules require this modifier.
`QY`	Medical direction of one CRNA by anesthesiologist	Use when an anesthesiologist medically directed a CRNA during transport.
`ET`	Use of stretcher van service (local code variant)	Use only when combined billing or specific payer rules distinguish stretcher/air ambulance modalities.
`AS`	Physician assistant, nurse practitioner, or clinical nurse specialist services	Use when a midlevel clinician’s services are reported in conjunction with transport-related billing according to payer rules.

Taxonomy Code	Specialty	Notes
`208U00000X`	Emergency Medicine Physician	Physicians who direct or receive critical patients during air transport and provide oversight of triage and handoff.
`225100000X`	Flight Nurse	Registered nurses specialized in aeromedical transport and critical care during rotary-wing missions.
`338N00000X`	Flight Paramedic	Paramedics certified in critical care and aviation medicine who provide prehospital interventions in-flight.
`207L00000X`	Anesthesiology	Anesthesiologists providing airway management or anesthesia-level support during transport when required.
`163W00000X`	Trauma Surgery	Trauma surgeons at receiving centers who coordinate care for severely injured patients transported by rotor wing.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`S32.011A`	Fracture of first lumbar vertebra, initial encounter for closed fracture	High-energy trauma with potential spinal instability prompting rapid air transport to trauma center.
`S72.001A`	Fracture of unspecified part of neck of right femur, initial encounter for closed fracture	Major orthopedic injuries often require rapid transfer for operative management at tertiary centers.
`I97.120`	Intraoperative hemorrhage and hematoma of aorta following a procedure	Vascular catastrophes that necessitate emergent transfer by air for definitive vascular surgery.
`R57.0`	Cardiogenic shock	Hemodynamic instability requiring advanced monitoring and expedited transfer to higher level of care.
`T81.11XA`	Hemorrhage complicating a procedure, initial encounter	Post-procedural bleeding requiring emergent transfer for intervention.
`A41.9`	Sepsis, unspecified organism	Severe sepsis or septic shock where time-critical transfer to an ICU or specialty center is required.
`G93.89`	Other specified disorders of brain	Acute neurological events (e.g., large hemorrhagic stroke) that may prompt rotor-wing transfer to a stroke center.
`I21.9`	Acute myocardial infarction, unspecified	Large acute MIs requiring rapid transport for percutaneous coronary intervention at a capable center.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`31500`	Intubation, endotracheal, emergency procedure	Performed before or during rotary-wing transport for airway protection in unstable trauma or respiratory failure.
`36415`	Collection of venous blood by venipuncture	Commonly performed preflight or in-flight for laboratory testing, crossmatch, or point-of-care analysis.
`36556`	Insertion of non-tunneled centrally-inserted central venous catheter; age 5 years or older	May be performed prior to or immediately after transport for hemodynamic monitoring or administration of vasoactive agents.
`96372`	Therapeutic, prophylactic, or diagnostic injection (subcutaneous or intramuscular)	Used for medications administered en route such as analgesics, anticoagulants, or other injections.
`94060`	Continuous monitoring of respiratory status by pulse oximetry and/or capnography for higher level monitoring	Represents advanced physiologic monitoring provided during flight when billed separately per payer rules.
`99291`	Critical care, evaluation and management of the critically ill or critically injured patient; first 30-74 minutes	Represents critical care time provided by clinicians that may overlap with transport care in documentation and billing workflow.

HCPCS A0021: Ambulance Service Outside State, Per-Mile Transport

HCPCS-A0080-VOLUNTEER-NON-EMERGENCY-TRANSPORTATION-MILEAGE

HCPCS Level II A0080: Non-Emergency Volunteer Transportation, Per Mile

HCPCS-A0090-NON-EMERGENCY-TRANSPORTATION-MILE-PRIVATE-VEHICLE

HCPCS A0090: Non-Emergency Transportation, Per Mile (Private Vehicle)

HCPCS-A0100-NON-EMERGENCY-TAXI-TRANSPORTATION

HCPCS A0100: Non-Emergency Transportation, Taxi

HCPCS-A0110-NON-EMERGENCY-BUS-TRANSPORTATION

HCPCS A0110: Non-Emergency Bus or Carrier Transportation

HCPCS-A0120-NON-EMERGENCY-MINI-BUS-TRANSPORTATION

HCPCS A0120: Non-Emergency Mini-Bus and Specialized Transport

HCPCS-A0130-WHEELCHAIR-VAN-NON-EMERGENCY-TRANSPORTATION

HCPCS Level II A0130: Non-Emergency Wheelchair Van Transport

HCPCS-A0140-NON-EMERGENCY-AIR-TRANSPORTATION

HCPCS A0140: Non-Emergency Air Transportation (Private or Commercial)

HCPCS-A0160-NON-EMERGENCY-TRANSPORTATION-CASE-WORKER-SOCIAL-WORKER-PER-MILE

HCPCS A0160: Non-Emergency Transportation Per Mile by Case or Social Worker

HCPCS-A0180-ANCILLARY-LODGING-NON-EMERGENCY-TRANSPORTATION

HCPCS A0180: Non-Emergency Transportation Ancillary Lodging

Showing 1–10 of 40

References

1.CPT® Codes and Descriptions. AAPC. Retrieved Jul 29, 2026.
2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Jul 29, 2026.
3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Jul 29, 2026.

Published by

Trek Health powers OpenPayer with a leading commercial payer intelligence platform, seamlessly converting fragmented payer data into actionable insights for provider organizations.

Trek Health ingests and normalizes Transparency in Coverage data and payer policy updates to give provider organizations a clear view of how commercial reimbursement behaves across markets, payers, and services. Our platform transforms raw payer disclosures into structured intelligence that supports contract evaluation, payer negotiations, and service line strategy. By combining market benchmarks with ongoing policy visibility, Trek helps teams identify variability, risk, and opportunity in commercial reimbursement. The result is faster insight, stronger negotiating positions, and more informed financial decisions.

Clinical & Coding Specifications

Clinical Context

Coding Specifications

Modifier	Description	When to Use
`22`	Increased procedural service	Use when the rotary-wing transport required substantially greater resources or time than usual due to patient complexity (document rationale).
`23`	Unusual anesthesia	Use if the patient required general anesthesia provided by the flight team during transport (rare for air ambulance but applicable if anesthesia-level care provided).
`52`	Reduced services	Use when the transport was partially completed or services were reduced compared to full service.
`53`	Discontinued procedure	Use if the flight was aborted for medical or safety reasons after initiation.
`76`	Repeat procedure by same provider	Use if the same air ambulance provider performed a repeat one-way transport for the same patient on the same date.
`78`	Return to operating/procedure room	Use if the transport was immediately followed by return to surgery or interventional procedure and indicates relatedness to prior procedure.
`80`	Assistant surgeon	Not typically used with `A0431`; include only when billing combined services that require reporting of assistant involvement.
`82`	Assistant (when qualified resident not available)	Use in rare cases where an assistant surgeon qualifier is required alongside other procedural reporting.
`QK`	Medical direction of two to four concurrent anesthesia procedures	Use only if applicable for billed anesthesia services provided during transport and medical direction rules apply.
`QX`	CRNA service with medical direction by physician	Use when a CRNA provided anesthesia-level care during transport with physician supervision and attribution rules require this modifier.
`QY`	Medical direction of one CRNA by anesthesiologist	Use when an anesthesiologist medically directed a CRNA during transport.
`ET`	Use of stretcher van service (local code variant)	Use only when combined billing or specific payer rules distinguish stretcher/air ambulance modalities.
`AS`	Physician assistant, nurse practitioner, or clinical nurse specialist services	Use when a midlevel clinician’s services are reported in conjunction with transport-related billing according to payer rules.

Taxonomy Code	Specialty	Notes
`208U00000X`	Emergency Medicine Physician	Physicians who direct or receive critical patients during air transport and provide oversight of triage and handoff.
`225100000X`	Flight Nurse	Registered nurses specialized in aeromedical transport and critical care during rotary-wing missions.
`338N00000X`	Flight Paramedic	Paramedics certified in critical care and aviation medicine who provide prehospital interventions in-flight.
`207L00000X`	Anesthesiology	Anesthesiologists providing airway management or anesthesia-level support during transport when required.
`163W00000X`	Trauma Surgery	Trauma surgeons at receiving centers who coordinate care for severely injured patients transported by rotor wing.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`S32.011A`	Fracture of first lumbar vertebra, initial encounter for closed fracture	High-energy trauma with potential spinal instability prompting rapid air transport to trauma center.
`S72.001A`	Fracture of unspecified part of neck of right femur, initial encounter for closed fracture	Major orthopedic injuries often require rapid transfer for operative management at tertiary centers.
`I97.120`	Intraoperative hemorrhage and hematoma of aorta following a procedure	Vascular catastrophes that necessitate emergent transfer by air for definitive vascular surgery.
`R57.0`	Cardiogenic shock	Hemodynamic instability requiring advanced monitoring and expedited transfer to higher level of care.
`T81.11XA`	Hemorrhage complicating a procedure, initial encounter	Post-procedural bleeding requiring emergent transfer for intervention.
`A41.9`	Sepsis, unspecified organism	Severe sepsis or septic shock where time-critical transfer to an ICU or specialty center is required.
`G93.89`	Other specified disorders of brain	Acute neurological events (e.g., large hemorrhagic stroke) that may prompt rotor-wing transfer to a stroke center.
`I21.9`	Acute myocardial infarction, unspecified	Large acute MIs requiring rapid transport for percutaneous coronary intervention at a capable center.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`31500`	Intubation, endotracheal, emergency procedure	Performed before or during rotary-wing transport for airway protection in unstable trauma or respiratory failure.
`36415`	Collection of venous blood by venipuncture	Commonly performed preflight or in-flight for laboratory testing, crossmatch, or point-of-care analysis.
`36556`	Insertion of non-tunneled centrally-inserted central venous catheter; age 5 years or older	May be performed prior to or immediately after transport for hemodynamic monitoring or administration of vasoactive agents.
`96372`	Therapeutic, prophylactic, or diagnostic injection (subcutaneous or intramuscular)	Used for medications administered en route such as analgesics, anticoagulants, or other injections.
`94060`	Continuous monitoring of respiratory status by pulse oximetry and/or capnography for higher level monitoring	Represents advanced physiologic monitoring provided during flight when billed separately per payer rules.
`99291`	Critical care, evaluation and management of the critically ill or critically injured patient; first 30-74 minutes	Represents critical care time provided by clinicians that may overlap with transport care in documentation and billing workflow.

HCPCS A0021: Ambulance Service Outside State, Per-Mile Transport

HCPCS-A0080-VOLUNTEER-NON-EMERGENCY-TRANSPORTATION-MILEAGE

HCPCS Level II A0080: Non-Emergency Volunteer Transportation, Per Mile

HCPCS-A0090-NON-EMERGENCY-TRANSPORTATION-MILE-PRIVATE-VEHICLE

HCPCS A0090: Non-Emergency Transportation, Per Mile (Private Vehicle)

HCPCS-A0100-NON-EMERGENCY-TAXI-TRANSPORTATION

HCPCS A0100: Non-Emergency Transportation, Taxi

HCPCS-A0110-NON-EMERGENCY-BUS-TRANSPORTATION

HCPCS A0110: Non-Emergency Bus or Carrier Transportation

HCPCS-A0120-NON-EMERGENCY-MINI-BUS-TRANSPORTATION

HCPCS A0120: Non-Emergency Mini-Bus and Specialized Transport

HCPCS-A0130-WHEELCHAIR-VAN-NON-EMERGENCY-TRANSPORTATION

HCPCS Level II A0130: Non-Emergency Wheelchair Van Transport

HCPCS-A0140-NON-EMERGENCY-AIR-TRANSPORTATION

HCPCS A0140: Non-Emergency Air Transportation (Private or Commercial)

HCPCS-A0160-NON-EMERGENCY-TRANSPORTATION-CASE-WORKER-SOCIAL-WORKER-PER-MILE

HCPCS A0160: Non-Emergency Transportation Per Mile by Case or Social Worker

HCPCS-A0180-ANCILLARY-LODGING-NON-EMERGENCY-TRANSPORTATION

HCPCS A0180: Non-Emergency Transportation Ancillary Lodging

Showing 1–10 of 40

References

1.CPT® Codes and Descriptions. AAPC. Retrieved Jul 29, 2026.
2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Jul 29, 2026.
3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Jul 29, 2026.

Published by

Trek Health powers OpenPayer with a leading commercial payer intelligence platform, seamlessly converting fragmented payer data into actionable insights for provider organizations.

OpenPayer

HCPCS Level II A0431: Ambulance Service, Rotary-Wing Air Transport, One Way

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Billing Code Overview

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HCPCS Level II A0431: Ambulance Service, Rotary-Wing Air Transport, One Way

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Billing Code Overview

Clinical & Coding Specifications

Clinical Context

Coding Specifications

Related Diagnoses

Related CPT Codes

Related Codes

References

Clinical & Coding Specifications

Clinical Context

Coding Specifications

Related Diagnoses

Related CPT Codes

Related Codes

References