Can i run all 5 LED's or at least more than one per pin in order to miminmise the wiring inside the airplane?
Basically no not directly. The Arduino's output pins should not be run higher than about 30mA, at 40mA damage starts to happen. So unless you run them at lower than 20mA you have to use a transistor to boost the current. Even so each LED has to have its own series resistor.
If you have a higher voltage than 5V you can run several in series like this:-
If you have only 5V it is best to use just one LED and one resistor but you can still have them in parallel.
All the LED's will be steady on (no blinking required)
Do you need an Arduino for this?