Definition
A written authorization signed by an authorized flight instructor in a student pilot's logbook (and on the student pilot certificate, where applicable) that permits the student to act as pilot in command of a specific aircraft without an instructor on board. The endorsement is required by 14 CFR Part 61, must specify the make and model of aircraft, and is valid for a limited period (typically 90 days) before it must be renewed by an instructor who has flown with the student.
Plain English
A signed note from a flight instructor that gives a student pilot permission to fly a specific type of airplane alone. Without it, a student is not legally allowed to fly solo.
Context Anchor
Seen in student pilot logbooks, training records, and instructor supervision discussions before a student is allowed to conduct solo flight.
Derivation
Solo comes from the Italian word for 'alone,' originally a music term meaning a passage performed by one person. Endorsement comes from the Old French endosser, 'to write on the back of,' originally meaning to sign the back of a document to approve it. Together: a signed approval to fly alone.
Why Pilots Care
It is a legal requirement; a student may not fly solo without this endorsement in the logbook.
Intuition Check
Do not read endorsement as a casual thumbs-up. In aviation, a solo endorsement is a specific written authorization with legal effect and stated limits.
Example Sentence 1
Before the student's first solo flight, the instructor reviewed her performance, signed the solo endorsement in her logbook, and briefed her on the conditions under which it was valid.
Example Sentence 2
The student checked the logbook to confirm the solo endorsement was current before the cross-country solo flight.