Aviation English
Basic ATC

What is Unable?

Unable A phrase used by pilots to indicate they cannot comply with a specific instruction or clearance.

Source: ICAO Doc 9432, FAA PCG

How is “Unable” Used in Practice?

Pilot advises: 'Unable to comply with altitude restriction, request alternative.'

Certification Exam Relevance

ICAO Level 4ICAO Level 5ICAO Level 6EASA FCL.055

Who Needs to Know This Term?

  • Pilots
  • Air Traffic Controllers
  • Cabin Crew

Related Aviation English Terms

ClearedMaintainClimb toContinue

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Frequently Asked Questions

What is Unable?

A phrase used by pilots to indicate they cannot comply with a specific instruction or clearance.

Where can I learn this term for free?

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