United 1448, sounding confused, then radioed that they were near taxiway Kilo, and as they re-entered Runway 5R/23L, reported that "somebody just took off" overhead, referring to FedEx 1662 that had indeed just become airborne in very close proximity to the United aircraft. However, the controller appeared not to take this seriously, stating, "you shouldn't be anywhere near Kilo", and advised the United 1448 crew to hold position. United 1448 informed the tower that they were now on an active runway, which they mistakenly believed to be 23R/5L (inactive at the time). A moment later the pilot corrected himself, stating that they were on 5R/23L. United 1448's crew was told again to stand by, so the aircraft remained idle at the intersection of the active runway, while the controller cleared MetroJet 2998 for takeoff on the same runway. The United 1448 pilot immediately interjected to insist that the plane was on the active runway, which the controller denied, saying it was not an active runway. Meanwhile, the MetroJet pilot, having heard the exchange, realized there was confusion over the whereabouts of United 1448 and refused the takeoff clearance, stating, "We're staying clear of all runways until we figure this out."