Why require a minimum of 1500 hours to become an airline pilot?

Question

In the United States, under part 61 standards for pilot certifications, for a person to apply for an airline transport pilot certificate one of the aeronautical experience minimums is a minimum of 1500 hours total flight time. Most ICAO compliant countries require similar numbers. My first question on this would be why so many? It’s true that you want airline pilots to be experienced and no doubt I would not expect an airline to make someone a captain of a large, turbine airplane without a minimum of say 2000 hours with a lot of that being hard instrument and weather time but why require a first officer to need a minimum of 1500 hours for an ATP?

I’m aware prior to 2014 that the FAA allowed part 121 first officers to fly with only a commercial pilot’s license for the right seat and the 1500 hour rule only came about after the Colgan air crash in 2009. People argue that this is what is resulted in only one commercial airline fatality over the past 10 years. Still I wonder why an arbitrary number 1500 was chosen for an airline transport pilot certificate. Now I am also aware that this is not always the case. For instance graduates of approved part 141 schools can get a ATP with only 1200 hours TT with a aviation related associates degree, 1000 hours TT with an aviation related bachelor’s degree and military pilots with 750 hours TT can apply for an ATP directly. My only thoughts would be, if part 61 training is so terrible that it requires a person to put in 1500 hours in a Cessna prior to applying for an ATP, what makes an aviation bachelors program superior or military flight training as compared to it, and why not simply train pilots under parts 61 to the same standards as the military does?

EDIT

Some other thoughts on this topic: While the military does allow people to operate large turbine powered aircraft with FAR less that 1500 TT, they’re in a position where they simply have no other alternative. You can’t give a fresh 2nd Lieutenant 1500 hours in a T-6 or T-38 prior to dispatching him/her to an F-16 squadron somewhere as it’s simply not affordable. Even these trainer aircraft cost several thousand an hour to operate and training budgets are already tight. So they’re sent off to a active unit with 200 to 300 hours total time. The downside is that, even in peacetime, military aviation units suffer horrendously high accident rates as opposed to their Part 121 counterparts. As I understand it, the USAF alone had 39 class 1 mishaps in 2018. It’s an unfortunate fact that, as much as primary flight training could teach you, it’s only a license to practice your craft; flying is an artform and takes a lifetime to master and there are a lot of dangers out there. That being said, mass hours alone are really not good experience. It requires APPLICABLE experience to matter. An aviator trained in a small part 61 flight school in central Iowa and logs 1500 hours flying Cessnas locally as a CFI is nowhere near ready for the rigors and stress of an airline pilot, but a pilot with 500-600 hours TT with complex, instrument, and multi-engine turbine time in high density airspace around major cities is far more likely to success here.

It bothers me that these kinds of regulations are written this way, without any thought to the practicality of it. It’s also strange that way, since, most of the FARs are very practical and based on well researched information as well as accidents in the past. It also bothers me that it causes new pilots to bear an extreme burden to build those kinds of flight hours for a career, which may or may not be beneficial to them. I’m just curious what the FAA’s thought process was in recommending the scheme

Answer 1

If I understand correctly, your main focus is the history of 61.159 and the literal question in your title: why does the FAA require 1500hrs for an ATP?

The short answer is that the FAA was complying with ICAO's ATP requirements. This is from the Federal Register in 2009:

International Compatibility

In keeping with U.S. obligations under the Convention on International Civil Aviation, it is FAA policy to comply with International Civil Aviation Organization (ICAO) Standards and Recommended Practices to the maximum extent practicable. There is one revision in this final rule document (See Revision No. 71) where the FAA has amended § 61.159(d) and (e) to conform our ATP certification requirements to ICAO Standards and Recommended Practices.

Here's the specific 1500hr requirement:

The current FAA regulation applies an obsolete ICAO ATP airplane aeronautical experience rule. Before 1974, ICAO only required 1,200 hours of total flight time to qualify for an ATP certificate in the airplane category. In 1974, ICAO amended its ATP aeronautical experience requirements for the airplane category to require 1,500 hours of flight time as a pilot [...] This revised change harmonizes FAA regulations to ICAO's current standard.

There were a few other changes for ICAO compliance in the same rule. And before you ask, I have no idea why ICAO chose 1500hrs :-)

You also asked why a first officer requires 1500hrs. As you mentioned, that was in response to the Colgan Air Flight 3407 crash but it was a political decision by Congress and didn't originate with the FAA. From the Federal Register again:

The Airline Safety and Federal Aviation Administration Extension Act of 2010 (Pub. L. 111-216) directed the FAA to conduct a rulemaking to improve the qualifications and training for pilots serving in air carrier operations. Specifically, section 216 of the Act focused on the qualifications of air carrier pilots and directed the FAA to issue a rule that would require all pilots serving in part 121 air carrier operations to hold an ATP certificate by August 2, 2013.

[...]

Section 217 also directed the FAA to ensure pilots have sufficient flight hours in difficult operational conditions that may be encountered in air carrier operations and stated that the minimum total flight hours to be qualified for an ATP certificate shall be at least 1,500 flight hours.

The wording of section 217 of the Act includes:

(1) Numbers of flight hours.--The total flight hours required by the Administrator under subsection (b)(1) shall be at least 1,500 flight hours.

That change seems to be largely due to lobbying by the families of the crash victims, who include it on their website as a "legislative accomplishment". I couldn't easily find any more detailed sources about why they made that specific point a goal.

I realize that this doesn't explain why ICAO wanted 1500hrs, or why the FAA previously wanted 1200hrs. The Federal Register online only goes back to 1994 and it would likely take some more 'serious' research to find out more about their original reasoning.