Inability to schedule flights between MMD-KTD airport for some aircraft types

MMD and KTD are two airports very close to each others (12 km apart), but are not considered serving the same city both in AS and in real life, because the two airports are on two separated islands. And in real life there’re also flights that connect the two islands together.

However, in AS, if user try to schedule a flight between the two islands, it could result in error due to “aircraft performance”. After some tests, it is found out that, using Dash 8-400A as example, because of the way the game calculate speed of the aircraft,
if the flight is set to be 25 minutes long, the flight speed will be displayed as 0km/h,
if the flight is set to be 26 minutes long, then the flight speed will become 720km/h, which is too fast for the aircraft type
while if the flight is set to be 27 minutes long, the flight speed will become 360km/h, which is too slow for the aircraft type.

Therefore, it seems like it would require an aircraft which speed is either around 720km/h or 360km/h for such flight to be allowed to operate in AS, which seems quite unrealistic.

It’s a known issue, see the second half of this post.

I think the problem here is for short flight within like 200 or so km, the aircraft would neither hit cruise altitude nor cruise speed during the flight, therefore instead of static duration for take off + landing, in case the system detected the flight to be created is a short flight, it should make use of another algorithm to compute the time and fuel needed.

That is pretty much what the paragraph I referred to above says.