Straight to the references:
Greater Flying Carpet (Mordenkainen's Magnificent Emporium p85)
A greater flying carpet carries creatures and objects at a speed of fly 6 and can hover. A character on the carpet can mentally command it to fly as a move action. (...) If more than one character on the carpet attempts to mentally command it, the carpet responds to each command in turn according to the characters’ initiative order.
Exploration Speed Nothing specific to quote, just providing a reference to the entry in the compendium for your reading pleasure.
So what is the exploration speed for the pair of riders (assuming no other companions are present to slow them down)?