It was around the time Nova betrayed Galactus. Since big G got really fed up with having a number of heralds turning on him due to their conscience he specifically chose a psycopath named Morg for his next herald. After witnessing some of Morg's heinous acts Surfer teamed up with Firelord and Nova to confront him and to force Galactus to choose a different herald.
In order to find Galactus, the three heralds dug up Gabriel, repaired him and revived him by charging up his "cosmic cells".
Then there was an awesome confrontation with Morg and Galactus with Terrax thrown in there as well, which resulted in Nova's death. But after that Airwalker pretty much hung around in space until Annihilation.