This is a critical piece of the puzzle and I love that you pointed it out. Bare necessities aside (shelter, food, etc), we start out with a set of win conditions (from parents, friends, etc), but ultimately we can determine them ourselves. In most democracies, nobody can tell you how to live your life.
The majority of airplanes are equipped with HEPA filters. As in, removing 99,97% of particles over 0.3 micron in size. The unfiltered air is fed in from the outside. It’s pretty clean and not a consideration for allergens like peanut particles.
Source: https://www.nationalgeographic.com/travel/article/how-clean-is-the-air-on-your-airplane-coronavirus-cvd