I have gotten sick after nearly every 8+ hour plane flight I've been on over the past few years, nearly every time. I started being very attentive to hand hygiene of late, before the COVID thing. And I might be catching whatever in the airport of course, or in the country because I'm not up to speed with their germs. If I use the head, I really clean up when I get back to my seat, gel on hands and wipe down surfaces in seating area. A less than two hour flight I wouldn't get up.