Gajeel had fought Panther Lily, who possess the ability of flight with his magic. During their battle, Gajeel was shown capable of performing very high leaps from the ground located several meters below him, to engage in midair confrontations with Lily, who was flying in midair because of his Aera. He bombarded Lily with a barrage of punches, then a roar, which blew a hole through the floating island.
This is the same magic which allowed Happy to to fly at great speed.
Lily is fast enough to evade some of Azuma's attacks. And Azuma is able to clash evenly with Mira and Erza during Tenrou Island arc, even getting the upperhand over them on several instances.
Gajeel's ability to close the distance quickly and past performance against foes with power of flight, should render Mira's aerial advantage a non-factor. Mira's strength also pales in comparison to Gajeel, who has shown he is strong enough to destroy a giant magical sword with his bare hands. And pinned down and hold still a giant, mechanical dragon constructed out of reinforced armour all by himself.
Gajeel completely outpace and overwhelm Bloodman towards the end of the fight, eventually killing him. Mira has not shown the same level of strength.