You’re mistaken. You do not have to take off with them. They are just there to make the map look cool and have an added feature that lets players use them. Actual planes still spawn in the air from the beginning of the match.
It definitely will not only be 10 seconds added. Have you ever tried landing and taking off on the carrier? To take off, drop load, turn around and land and then to take off again is like a 4 or 5 minute ordeal. It takes roughly 1-2 minutes to get up to a good speed and altitude from taking off. Tanks also have the pleasure of staying in the fight for quite some time before reloading. Planes have to re arm every pass or 2