B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 275
Communication Breakdown; Situational Awareness
ATC Issue All Types; Deviation / Discrepancy - Procedural Clearance; Ground Incursion Runway
Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented
Human Factors; Procedure
Approaching the end of A [Alpha] taxiway for takeoff on 12R; monitoring Tower on freq 118.1; I instructed my FO [First Officer] to contact Tower for takeoff clearance. FO contacted Tower and what we believed was 'cleared for takeoff contact 118.6 for departure' was not our instruction; what Tower instructed us to do was to contact Tower on freq 118.6 for takeoff.My experience in Cancun was that when issued takeoff clearance; Tower clears you for takeoff and instructs you to contact Departure Control on xxx.x frequency. So when I heard what I anticipated to be takeoff clearance and contract Departure on 118.6; I assumed we were cleared for takeoff and freq 118.6 was our Departure frequency.It was during takeoff roll above 80 knots when my FO made contact with what we thought was Departure Control on 118.6 that we realized we were on a different Tower frequency and not on Departure frequency. Tower cleared us to continue and contact Departure Control airborne.
Approaching runway hold short lines; I switched frequency to 118.6 and stated 'Company on the roll 12R' and got no response. Captain advanced throttles for takeoff stated 'set takeoff thrust' I stated 'thrust set'. The Captain said 'That must be our new Departure frequency'. I made my 80 knot call out; reached down; swapped frequency back to 118.1; Tower said we were 'not cleared for takeoff'; I stated 'we were cleared for takeoff'; Captain stated 'be quiet'. From that point on; there was no communication between us and Tower. We switched over to Departure frequency at 1400 feet; we were cleared to climb to FL 200; and then cleared to our next waypoint.Just want to point out that it was a very light day. No outside distractions; we pushed on time; we were not being rushed in any way; and the weather was good. When we got up to cruising altitude; the Captain and I talked about it and we both heard that we were cleared for takeoff.
B737 flight crew reported taking off without a clearance at MMUN following a confusing message from Tower.