How do you select or unlock plane variants?

In Battlefield 1, there are three classes of plane: Fighter, Attack, and Bomber. But each class has 3 variants, see this link: http://www.bfcentral.net/bf1/battlefield-1-planes/

For instance, the Fighter class has Dog Fighter, Bomber Killer, and Trench Fighter. If I choose a Fighter plane, by default Dog Fighter is selected. To select one of the two other variants, do I need to unlock with War Bonds, or are they selectable in some way from the menu?

Solution 1:

Apparently, based on posts in this thread, plane (and tank) loadouts can be changed when a vehicle is available by using the Customize option. This includes changing variants of vehicles. However, other players can hop into these vehicles and drive off with them while you are customizing your loadout, which means you won't get to use the vehicle.

You need to select/highlight the tank/aircraft icon on the spawn screen. If tank/aircraft spawns aren't available, you can't change tanker/pilot loadout.

I was able to customize a tank last night. It's on the spawn screen. Once your cursor is locked onto an available tank you can press the same customize button you would use to customize your medic. I was able to buy the Frommer Stop Auto pistol for main weapon and unlock the two other types of tank (flamethrower and breakthrough I think). You have to be very quick though.

Based on this post, however:

I use empty server sometimes.

And the replies to it, it sounds like your customization choices are permanent until you alter them again. Thus, if you want to customize your loadout without worrying about losing the vehicle, you can go to an empty or unpopulated server and take your sweet time customizing and weighing your options for your vehicle loadouts.

Solution 2:

After some searching, I found that using the Battlefield Companion app was the easiest way to purchase the unlocks with War Bonds.

Career -> Select BF1 -> Customize Loadout -> Swipe over to Vehicles