If i made you mad i didnt know im sorry

@Himynameiswalrus XD how about no.....
they said that they have problem with the MP ... which was recently solved by @UnstableOrbit and @HellFireKoder
and devs are now interested in their project and MAYBE it wont be an external mod but an in-game feature... but hey mod or not it's still multiplayer and those 2 modders said they will release it no matter devs want to take it or not

@Mox ugh! Fine

@MechWARRIOR57 send me links

@Mox 2 times

@MechWARRIOR57 how many times have I scolded you?

@Mox so? Jeez It's like I can't say anything without you scolding me

It is possible.
Someone did it already themselves. VIDEO

The major hurdles for an official release would be framerate, synchronicity, and dedicated server maintenance.
You could probably keep the lag down by making the game generate special models for MP that are only a single piece. That way the game has to only draw one object per player. Anyone who has tried spawning in several planes with high part-counts at once knows how much that would help.
As for synchronicity, all you need is a good netcode. The devs would probably need to outsource to find the help they need for that if they don't have the know-how for it.
Finally, the most important factor in making a game multiplayer is keeping servers running. Dedicated game servers can be pretty expensive, and letting the community establish and maintain servers can be unreliable.
An official MP release is probably far off.

The developers have said that in order to implement this feature into the game, they would have to recode pretty much the entire game. Thus, they will not add it into SimplePlanes. But perhaps, if SimplePlanes 2 ever comes out, they will try to implement this.
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@MechWARRIOR57 you don't have to be so rude... He's a new user and doesn't know any better.

@Himynameiswalrus so stop this clogs up the forums by making useless forums when you should know it will never come so STOP

The devs confirmed that it will not happen a million times