Interior differences

There are also some differences that you'll only notice when inside the plane. 

Cockpit: Boeing and Airbus planes are flown very differently. Airbus planes are flown with sidesticks (which look like levers) while Boeing planes are flown with yokes (which look like steering wheels). The seats in the cockpit are also usually space further apart. If you are able to get a quick peek at the cockpit, this is usually a dead giveaway

Exit doors: The exit doors on a Boeing plane are opened with a lever that you turn clockwise. Exit doors on an Airbus plane are opened by pushing a lever upwards