Narrative:

Level at FL270, awaiting climb clearance. We were cleared to FL280. The autoplt was not engaged as I was hand flying the airplane. I (captain flying) thought the assigned altitude was FL290. Passing FL283, the first officer stated '1000 ft to go' when the altitude alert buzzed. Neither of us realized that was the warning that we were 300 ft high. I continued the climb until approaching FL290, at which time I noticed the altitude alert flashing. I crosschecked the assigned altitude window (28000 ft), realizing then that I had climbed to the wrong altitude. At about the same time, ATC called and said our assigned altitude was FL280. The controller then assigned us a 30 degree turn to the left and return to FL280. I complied with his directive. When we leveled off at FL280, he cleared us direct to el paso. I noted on the TCASII as we leveled off at FL280 that there were no targets on the TCASII screen, ie, no traffic within 15 mi, thus, no conflict existed. I asked the controller if I needed to call someone about the altitude deviation. He said it was not a problem. This incident could have been avoided had I been using the autoplt. I was most fortunate that another aircraft was not close enough to create a conflict. I will be hand-flying the aircraft much less in the future.

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Original NASA ASRS Text

Title: B737 FLT CREW CLBS ABOVE ASSIGNED ALT AT FL280 WITH ZAB.

Narrative: LEVEL AT FL270, AWAITING CLB CLRNC. WE WERE CLRED TO FL280. THE AUTOPLT WAS NOT ENGAGED AS I WAS HAND FLYING THE AIRPLANE. I (CAPT FLYING) THOUGHT THE ASSIGNED ALT WAS FL290. PASSING FL283, THE FO STATED '1000 FT TO GO' WHEN THE ALT ALERT BUZZED. NEITHER OF US REALIZED THAT WAS THE WARNING THAT WE WERE 300 FT HIGH. I CONTINUED THE CLB UNTIL APCHING FL290, AT WHICH TIME I NOTICED THE ALT ALERT FLASHING. I XCHKED THE ASSIGNED ALT WINDOW (28000 FT), REALIZING THEN THAT I HAD CLBED TO THE WRONG ALT. AT ABOUT THE SAME TIME, ATC CALLED AND SAID OUR ASSIGNED ALT WAS FL280. THE CTLR THEN ASSIGNED US A 30 DEG TURN TO THE L AND RETURN TO FL280. I COMPLIED WITH HIS DIRECTIVE. WHEN WE LEVELED OFF AT FL280, HE CLRED US DIRECT TO EL PASO. I NOTED ON THE TCASII AS WE LEVELED OFF AT FL280 THAT THERE WERE NO TARGETS ON THE TCASII SCREEN, IE, NO TFC WITHIN 15 MI, THUS, NO CONFLICT EXISTED. I ASKED THE CTLR IF I NEEDED TO CALL SOMEONE ABOUT THE ALTDEV. HE SAID IT WAS NOT A PROB. THIS INCIDENT COULD HAVE BEEN AVOIDED HAD I BEEN USING THE AUTOPLT. I WAS MOST FORTUNATE THAT ANOTHER ACFT WAS NOT CLOSE ENOUGH TO CREATE A CONFLICT. I WILL BE HAND-FLYING THE ACFT MUCH LESS IN THE FUTURE.

Data retrieved from NASA's ASRS site as of July 2007 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.