Originally Posted by
SunLover
I would suggest you sit together on the two seat side and put the arm rest up after takeoff. That way they can spread out and feel more comfortable about the space invasion since it is not happening to a stranger. Or just purchase two seats for your friend to use alone to begin with.
SunLover
+1
If in doubt, then please do not buy one seat next to an unknown passenger. If you are perfectly comfortable sitting next to your acquaintance, then do so. If you are not perfectly comfortable sitting next to her, then it's probably a good idea to buy 2 seats.
Regardless of UA's official policy, there is also common courtesy to consider. If any part of a passenger's body extends beyond the armrest and into the next seat, then they are taking space that another passenger has paid for and is expecting to be able to use.