I am currently sitting on a JetBlue flight, and am getting 8 Mbps down and 0.5 Mbps up. There are 140 seats on the plane, if we assume half of them use Wi-Fi, and performance degrades to 5 Mbps down with that many users, you get to 350 Mbps. Other stuff like the live TV also goes over the satellite connection I believe.

JetBlue used to have two tiers (free browsing and paid streaming) but that seems to be gone now; I’m on an A220 with Viasat 2.