Narrative:

Bottom line up front: [we diverted] for a suspected fuel leak. We pushed back from the gate with 400 pounds extra fuel. We were supposed to have 12;800 pounds; but actually had 13;200 pounds. After takeoff; we requested the [flight plan projection] and it showed we were planned to land with 7;300 pounds.[enroute]; we checked the actual fuel against the [flight plan projection]. We discovered we had 1;100 pounds less fuel than planned. The captain and I discussed the possibility of a fuel leak and began watching the fuel consumption closely. We ran the fuel leak checklist in the A319 QRH. We looked at the fuel quantities. The outer tanks were full. The left and right inner tanks showed 3;500 and 4;140 pounds respectively. The left and right fuel flows were 2;480 and 2;560 pph respectively. We acknowledged with these fuel flows; the right inner tank quantity should have been lower than the left; or at least even. As we continued to monitor the quantities; we noticed the left inner tank quantity continued to decrease slightly faster than the right.the captain called [maintenance] and discussed the problem with them. Then we discussed our options and agreed we should divert; because we felt we did not have enough fuel to safely continue to [destination]. We were close to [the alternate airport]. We [advised] ATC and got routing instructions for our divert. We joined the arrival and the captain flew a visual approach to a landing. We pulled off to the south side of the runway and met the arff. They inspected the aircraft and told us we had no visible fuel leaks. We then taxied to the gate. Upon engine shutdown; we had no fuel in our outer tanks. The left and right inner tanks showed 2;620 and 3;360 respectively. Again; we were supposed to land [at destination] with 7;300 pounds of fuel; but we shut down [at the closer alternate] with 6;000 pounds.as a side note; after [advising ATC]; ATC assigned us to descend to 10;000 feet. In our descent; ATC notified us to hold 10;000 feet and we noticed we were descending below that altitude. We stopped our descent 500 feet below and quickly climbed back to 10;000 feet. We then continued the remainder of the arrival and approach to landing without incident.

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Original NASA ASRS Text

Title: Airbus A319 First Officer reported diverting to an alternate airport after noticing a probable fuel leak.

Narrative: Bottom line up front: [we diverted] for a suspected fuel leak. We pushed back from the gate with 400 pounds extra fuel. We were supposed to have 12;800 pounds; but actually had 13;200 pounds. After takeoff; we requested the [flight plan projection] and it showed we were planned to land with 7;300 pounds.[Enroute]; we checked the actual fuel against the [flight plan projection]. We discovered we had 1;100 pounds less fuel than planned. The Captain and I discussed the possibility of a fuel leak and began watching the fuel consumption closely. We ran the Fuel Leak checklist in the A319 QRH. We looked at the fuel quantities. The outer tanks were full. The left and right inner tanks showed 3;500 and 4;140 pounds respectively. The left and right fuel flows were 2;480 and 2;560 PPH respectively. We acknowledged with these fuel flows; the right inner tank quantity should have been lower than the left; or at least even. As we continued to monitor the quantities; we noticed the left inner tank quantity continued to decrease slightly faster than the right.The Captain called [Maintenance] and discussed the problem with them. Then we discussed our options and agreed we should divert; because we felt we did not have enough fuel to safely continue to [destination]. We were close to [the alternate airport]. We [advised] ATC and got routing instructions for our divert. We joined the arrival and the Captain flew a visual approach to a landing. We pulled off to the south side of the runway and met the ARFF. They inspected the aircraft and told us we had no visible fuel leaks. We then taxied to the gate. Upon engine shutdown; we had no fuel in our outer tanks. The left and right inner tanks showed 2;620 and 3;360 respectively. Again; we were supposed to land [at destination] with 7;300 pounds of fuel; but we shut down [at the closer alternate] with 6;000 pounds.As a side note; after [advising ATC]; ATC assigned us to descend to 10;000 feet. In our descent; ATC notified us to hold 10;000 feet and we noticed we were descending below that altitude. We stopped our descent 500 feet below and quickly climbed back to 10;000 feet. We then continued the remainder of the arrival and approach to landing without incident.

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.