

OpenTyrian. Classic DOS shmup made free and ported to Android long ago.
https://play.google.com/store/apps/details?id=com.googlecode.opentyrian
SuperTux had an Android port for ages, but they delisted it from Play Store for some reason. You still can get .apk file here:
https://sourceforge.net/projects/libsdl-android/files/apk/SuperTux/
Time savings in today’s economics would be completely negated by waiting two hours in line at the airport.