a1) 'All aircraft types' - Lists, on the right side, all aircraft types, regardless of the type of aircraft selected on the left side.
a2) 'Same aircraft type' - Lists, on the right side, only aircraft that match the type of aircraft selected on the left side.
- if a helicopter is selected on the left side, then on the right side, only helicopters are listed.
- if a small aeroplane is selected on the left side, then on the right side, only small aeroplanes are listed.
- if a large aeroplane is selected on the left side, then on the right side, only large aeroplanes are listed.
a3) 'Helicopter' - Lists, on the right side, only helicopters, regardless of the type of aircraft selected on the left side.
a4) 'Small aeroplane' - Lists, on the right side, only small aeroplanes, regardless of the type of aircraft selected on the left side.
a5) 'Large aeroplane' - Lists, on the right side, only large aeroplanes, regardless of the type of aircraft selected on the left side.
b) This allows helicopters to be autoreplaced with aeroplanes and vice versa. Failure to do so would mean the replacement is being done in an incompatible hangar, but at least the possibility is there.
Screenshot valid for v1:
