It is both a question of what to put on the app, but also how to describe it.

One of the most simple things that gets looked at is attention to detail; being consistent on how you write down names (first and last? first, initial, last? first initial and last?), consistent format in supervisor/reference phone numbers (xxx-xxxx, or (xxx) xxx-xxxx, or xxx.xxx.xxxx, etc), consistent in how you write addresses of past jobs. Reportedly there is an an aspect of this attention to detail and consistency in deciding who they call to interview.

Another part that gets attention is the "duties" section of the various entries in the Employment History section. They're looking for more detailed explanations of job duties in there than most people actually provide. As an example, I worked in FBO line service while I was in college, and before the reviews I had a simple one-line duty explanation about fueling airplanes. After both reviews, it ended up looking like this:

"All aspects of aircraft service, including greeting, parking, fueling, de-fueling, towing, loading, unloading, servicing, and cleaning. General customer service for corporate, commercial, and private aircraft operators and passengers. Operation and service of aircraft fueling vehicles and ground support equipment, power carts, lavatory service carts, tugs, towbars and towing devices. Abide by all FAA and company requirements for aircraft servicing, flight line safety and security procedures. Perform accounting and record keeping of services provided."

As another example, both of the companies I used spent time on the "Educational Achievements" and the "Achievements and Awards" sections. I had listed a couple things in each area using bullet points. Both companies had me add more to these areas, for example, adding many military awards from throughout my career (Quarterly/annual Top Guns, a MAJCOM Safety "well done" award, etc) and adding verbiage to describe what they were and what they meant.

Since, at the time, AirlineApps did not have a dedicated area to list volunteerism and community service, so there was also advice on where to list that and, like above, how to describe it.

Again, there are a lot of different aspects they look at and provide input on that most of us don't even know matter or make a difference. It is difficult to just list all of it in a forum post.