The sun was directly overhead when Mexico City Approach first picked up the transmission.
"Mexico City Approach, Nova Transit One, passing flight level two-eight-zero, descending, vertical approach profile, inbound Benito Juárez International."
The approach controller, a woman named Catalina who had been at her station since six in the morning, looked at her display.
The transponder return had appeared at the exact moment the transmission came through, with clean signal, correct squawk code and the callsign matching the pre-filed coordination notice exactly.
She was surprised that the space shuttle was actually communicating with the control tower, as this was the first time it has happened.
She didn't think too much about it and keyed her response. "Nova Transit One, Mexico City Approach, radar contact, descend and maintain flight level one-five-zero, proceed direct Juárez, expect landing zone clearance on tower frequency."
