Airplane Wi-Fi is great to have, but often, it's an expensive perk that you need to pay extra for when you're booking your tickets. If you're on T-Mobile, though, you might just get it as a perk if you're flying United.

Some eligible T-Mobile users will soon be able to enjoy free Wi-Fi on their United flights. The carrier already offered free connectivity on select flights from American Airlines, Alaska Airlines, and Delta, and United is the latest one to join the list.

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If you wanted to book flights on United, and you'd love to take advantage of some free Wi-Fi, the perk will be available this fall. The United Express fleet will not be eligible initially, but United Airlines says that availability for these flights will "soon follow." The promotion will also be locked to "eligible" T-Mobile customers, with no details on what that means. Most of T-Mobile's other in-flight Wi-Fi promotions are locked to Magenta and Magenta Max plans.

Neither United nor T-Mobile have offered precise dates for a rollout (and T-Mobile's in-flight Wi-Fi information website doesn't mention United support just yet), so we'll have to wait to know more.

Source: United Airlines