Provide what you think is relevant, significant....longer stays in countries outside of your residence. And, provide an explanation letter stating the fact that you were a pilot and travelled quite a lot - also that you are willing to give details if necessary. Not sure if your logbooks are filed/tracked, but maybe including the main page with your info and logbook number.
For example (resident of country X):
Country Y - Vacation - 15 days - DATE to DATE
Country A - Work (pilot) - Multiple entries - MONTH to MONTH (period when you flew here, not necessarily very specific)
Country B - Work (pilot) - ....same.....
Country Z - Visiting family - 30 days - DATE to DATE
I too was crew, but on cruise ships; while not as much, I still had quite a lot of travel that I couldnt all note. So, the system I used is the one I wrote above. I broke it out to countries and noted it was multiple entry. Provided an explanation letter, and included my crew card (used for entry - not passport), company contracts and other related immigration documents. Same would apply for EU passport holders who dont get stamped at border crossings. Just make sure to explain the reasons for not providing detail, and I'm positive they will understand. I'm also certain you wouldn't be the first to have applied with this background. Same as me...be ready to provide the logbook at their request though.
Hope that helps!