Star Wars X-Wing (2nd Ed): Hotshots and Aces Reinforcement Pack - Rules of Play says:

Enhance your squadron options and launch new pilots with the Hotshots and Aces Reinforcements Pack! With upgrades available to all factions and new pilots for numerous ships in the Rebel, Imperial, Scum, Resistance, and First Order factions, you can now add iconic characters like Leia Organa, Captain Phasma, and K-2SO to your squads.