Narrative:

We landed uneventfully on runway 16R at sea and cleared left onto taxiway 'P' and were instructed by ATC to hold short of runway 16C; which we did; along with two other aircraft. Tower cleared all three of us to cross runway 16C and hold short of runway 16L on 'P'. With all three of us cleared to cross and hold short on 'P' we could not clear the hold short line with our entire aircraft. There was a 757; then a regional; and then us; and we were all tightly spaced holding short of runway 16L. We were approximately 25 feet from the regional in front of us and he was closely spaced with the 757 in front of him. We were not completely across the runway clear/hold line; but we assumed (wrongly) that ATC could see us and knew he had us hanging into the clearway. We also thought that they were only taking off runway 16L; wrong.we heard tower clear an aircraft to taxi 'into position and hold runway 16C.' I asked the first officer to query tower and at that same moment an airliner passed behind us on takeoff. We had not heard him cleared for takeoff runway 16C on the tower frequency. After takeoff; the airplane on takeoff mentioned our being over the clear line when we were trying to get in touch with the tower at the same time. There was no clearance issue as our tail was well clear of the runway. Tower didn't acknowledge any of this after the reports but instead cleared all three aircraft to cross runway 16L and switch to ground.don't assume that ATC knows what they are doing and won't make any mistakes; and don't wait even a few seconds to query them about any weird situation.

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Original NASA ASRS Text

Title: A321 Captain reported the tail of his aircraft was not clear of the runway while takeoff operations on the same runway were still being conducted.

Narrative: We landed uneventfully on runway 16R at SEA and cleared left onto taxiway 'P' and were instructed by ATC to hold short of RWY 16C; which we did; along with two other aircraft. Tower cleared all three of us to cross runway 16C and hold short of RWY 16L on 'P'. With all three of us cleared to cross and hold short on 'P' we could not clear the hold short line with our entire aircraft. There was a 757; then a regional; and then us; and we were all tightly spaced holding short of RWY 16L. We were approximately 25 feet from the regional in front of us and he was closely spaced with the 757 in front of him. We were not completely across the RWY Clear/Hold Line; but we assumed (wrongly) that ATC could see us and knew he had us hanging into the clearway. We also thought that they were only taking off RWY 16L; wrong.We heard Tower clear an aircraft to taxi 'Into Position and Hold RWY 16C.' I asked the FO to query tower and at that same moment an airliner passed behind us on takeoff. We had not heard him cleared for takeoff RWY 16C on the tower frequency. After takeoff; the airplane on takeoff mentioned our being over the clear line when we were trying to get in touch with the Tower at the same time. There was no clearance issue as our tail was well clear of the runway. Tower didn't acknowledge any of this after the reports but instead cleared all three aircraft to cross runway 16L and switch to Ground.Don't assume that ATC knows what they are doing and won't make any mistakes; and don't wait even a few seconds to query them about any weird situation.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.