Medium Large Transport; Low Wing; 2 Turbojet Eng
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 124; Flight Crew Type 10800
Communication Breakdown; Confusion; Situational Awareness
ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued Advisory / Alert
Human Factors
Just prior to commencing the LOWBO 3 RNAV Arrival; we received a clearance to descend to FL290. Prior to BRMLY (the start of the arrival) we received clearance; 'After BRMLY cleared direct JOKLO; cross JOKLO at 15;000 ft.' Just prior to BRMLY we were given direct to JOKLO. While proceeding to JOKLO; ATC said something like; 'for now you can descend at Pilots Discretion to FL280.' Both the F/O and I interpreted this to mean; if we desired we could descend to FL280 but that the original crossing restriction of 15;000 ft at JOKLO was still applicable. This also made sense because BRMLY had a published crossing restriction of FL290. We simply thought that ATC was telling us we could descend out of FL290 since we were direct JOKLO. ATC never used any terminology as to 'amending' our clearance or Pilot Discretion 'maintain' FL280. Nor was our original crossing restriction at JOKLO at 15;000 ft cancelled. Passing FL265; ATC queried us if that was our correct altitude; because he had 'amended' our clearance to FL280. The FO replied that we interpreted his clearance as originally given to cross JOKLO at 15;000. What complicated matters was that ATC actually wanted us to stop at FL280; due to traffic at our 11 o'clock and below us. This was only passed to us after we had commenced our descent. We sighted the traffic and it was no factor visually or on the TCAS. ATC said nothing else and passed us on to the next Controller without any comment.
We were level at FL290 on the LOWBO 3 Arrival into ABQ when ABQ Center instructed us to cross JOKLO at 15;000 ft; I read back the instructions and the Captain dialed in 15;000 ft in altitude window. Shortly after ABQ Center said 'PD to FL280 now' which I read back. The Captain then read back 'PD 280 and cross JOKLO at 15;000 ft' which I agreed with. We started our descent when ABQ Center pointed out traffic at 11 o'clock which we had in sight. Out of approximately 26;500 ft; ABQ Center said 'I amended your altitude to FL280 and I see you're below that.' I told him what our interpretation of the clearance was and he said 'OK'. He then switched us to the next ABQ Center and the rest of the flight was uneventful.
While descending into ABQ on the LOWBO3 Arrival; there was a miscommunication between ATC and the flight crew about altitude cleared to.