Aviatrix:

Both Ryanair and Easyjet submit their schedule data in industry-standard SSIM format to the timetable co-ordinators. Go always used to do this and Easy carried the process on when they took them over.

But OAG has always reached out to the non-standard airlines (although not as well as the much-missed ABC World Airways Guide from the UK), and it must cost them a lot of staff time to do this. Virgin Atlantic amazingly do not follow the industry standard (apparently they just e-mail Excel spreadsheets to interested parties), and Southwest in the USA do not do so either. OAG have to get all this in manually. And there are many third-world and minor operators that do not do so. Some are in OAG, some not.

Back to the original question I use Electronic Travel Desk by Goldenware Travel Technologies which does give all the industry-standard details, and is up to date. These are the people who do both the Star Alliance and the OneWorld downloadable system timetables you can get from those airlines' websites; they have extended this as an independent product to give all the schedules they have access to. So all the US majors (except Southwest), and even most of Virgin Atlantic comes in under Continental codeshares.

http://www.lencom.com/desc/indexN9774.html