Most of our aircraft have animated doors. You can use these key combinations for opening them:
"SHIFT + E" usually the main door or pilot door
"SHIFT + E + 2" usually copilot door (if equipped)
"SHIFT + E + 3" usually the baggage compartment or cargo door (if equipped)
If an aircraft has only one door for all the passengers (like Piper Arrow for example), "SHIFT + E + 2" will be for the baggage area.
NOTE: the sequence for opening door is: press Shift+E, release them and inmediately press the number.