If you didn’t know about people infecting each other on planes, you haven’t been following the news very closely. There would have been far more such reports if it weren’t for people wearing masks and in some places requirements of proof of vaccination and/or a recent negative test.
Passenger A in this diagram, who was asymptompatic until a couple of days after the flight, infected at least four other passengers.
https://wwwnc.cdc.gov/eid/article/27/3/20-4714_article
You don’t have to sneeze or cough to spread Covid. Aerosols, not just droplets, remember?