In the USA:
Known as ATP or ATPL, the Airline Transport Pilot certificate is the highest grade certificate issued by the FAA. It is for pilots what a PhD is for Scientists.
Eligibility
To be eligible for an Airline Transport Pilot certificate, you must know English and:
Be at least 23 years of age; AND
Be of good moral character.
You must already hold one of the following pilot certificates:
If US certified: at least a commercial pilot with an instrument rating; OR
ICAO country: ATP or commercial pilot with an instrument rating, without limitations, subject to background check.
The experience required for an airplane ATP certificate is outlined below.
at least 1,500 hours of total time as a pilot
500 hours of CROSS-COUNTRY flight time
100 hours of NIGHT time or 75 hours + 45 full stop landings at night
75 hours of instrument flight time, or 50 flight + 25 simulator
* flight time - logged time between engine start and engine shutdown after a flight in an actual airplane
* simulator time - logged DUAL instruction in a certified flight simulator or flight training device representing an airplane
* cross country - trips of 50 NM and more can be logged and used for ATP experience purposes even without a landing (private pilot and commercial pilot cross-country requires a landing)
Thank you; that’s most helpful and eye-opening.