United Airlines said a key measure of revenue rose as much as 4.5 percent in June, a big improvement from a year earlier when it was still struggling with technology headaches.

United spent much of last spring and summer trying to sort out a shift to one large, combined computer system to handle functions that used to be done separately by United and Continental. Those two airlines merged in 2010 to form United Continental Holdings Inc.

The measure, passenger revenue per available seat mile, tracks how much money the airline collects per seat flown one mile. United estimated late Monday that it rose 3.5 percent to 4.5 percent in June.

Traffic fell 0.6 percent last month, led by a 2.4 percent drop in domestic traffic. International traffic rose 1.5 percent.

United cut more than enough flying capacity to match the decline in traffic, with available seat miles falling 2 percent. Domestic seats fell 3.7 percent, while international seat miles rose slightly.

Because United cut seats faster than traffic declined, its remaining flights were fuller. Occupancy rose 1.2 percentage points to 87.7 percent.

For the first half of the year, United traffic has fallen 1.4 percent. Capacity is down 3.5 percent. Occupancy has risen 1.7 percentage points, to 83 percent.

Photo Credit: United Airlines 787 Dreamliner jets are seen parked on the tarmac at George Bush Intercontinental Airport in Houston, Texas, January 17, 2013. Donna Carson / Reuters