In order to meet safety requirements, the airlines may deny your reservation or require you to travel with a companion for your own safety and that of other passengers. That person would be responsible for assisting you in the event of an emergency if you are unable to help yourself.
Generally, the people who are likely to need a companion are those who:
have a severe learning or cognitive disability which prevents them from understanding or reacting to safety instructions; or are both blind and deaf so they are unable to understand and react to safety instructions; or have a disability that prevents them from moving without assistance to reach an emergency exit.
To decide whether you are self-reliant or need to travel with a companion, think about whether you can manage the following activities without help. Can you:
fasten and unfasten your seat belt?
leave your seat and get yourself to an emergency exit (this does not need to be by walking)?
put on an oxygen mask?
lift yourself from a passenger seat to an on-board wheelchair?
use the toilet facilities unaided?
administer your own medicine?
breath without being reliant on supplementary oxygen?
If you do need someone to travel with you, that person must be over 18 years old and physically capable of helping you in an emergency. Such person can travel with a maximum of 2 passengers requiring additional special assistance.
If in doubt, please make sure that you contact the airline and ask if you would be required to have a carer travelling with you.