[WhiteGhost]

Код:

public OnPlayerEnterVehicle(playerid, vehicleid, ispassenger)
{
	if(GetVehicleModel(vehicleid == 81)
	{
	SendClientMessage(playerid, COLOR_YELLOW, "Your Tail Number is EA-6833");
	}

Btw dont you when the message sent to the player when hes in the vehicle?

https://sampwiki.blast.hk/wiki/OnPlayerEnterVehicle is called when a player is starts entering a vehicle,you should use
https://sampwiki.blast.hk/wiki/OnPlayerStateChange