Update : 4th May: I have changed to a newer hardware( ipad air M4 : 12Gig RAM onboard) . No more problem. That might explian why the crashing of the bigger airport and no issue with the smaller airport .Do that note its RAM( my older ipad 9th gen only have 3Gig of RAM) and not storage. However, it felt that its the newer functionality in verion3.5.1 eat up the RAM. I play HKG and BKK airport in the previous release , my older ipad DO NOT have any issue