Can I fly normally if I am over 80 years old with someone to accompany me?

I suggest you ask the airline company, each airline has different regulations, and some have special requirements for special elderly people (for example, with pacemakers, etc.).

If you are over 80 years old, you must be accompanied by someone on the plane. This is the regulation of the Civil Aviation Administration, so you can fly normally if you are accompanied by someone, but it is best to bring a health certificate. After all, if you are old, the flight staff will pay close attention to you if you fly by plane, so it would be better to have a health certificate and know the situation in advance

You have to ask the corresponding airline, after all, the rules are set by the airline.