CHARLOTTE, N.C. -- ( TheStreet) -- Airlines obsessively track and manage their on-time performance, and recently none have been more obsessive than Delta ( DAL)and US Airways ( LCC). That is because, throughout the year, the two carriers have been locked in a neck-and-neck battle for the best operational results among the four network carriers. The most recent report by the U.S. Transportation Department shows just how close they are. In the second quarter, 87.5% of Delta flights arrived on time, while 87.4% of US Airways flights arrived on time. In the first quarter, 87.3% of Delta flights arrived on time, while 87.2% of US Airways flights arrived on time. The DOT tracks operational metrics for 18 carriers. The most closely watched is A14, or arrivals within 14 minutes of schedule. Typically, operating on time enhances performance in the other key operational metrics, mishandled bag rates and customer complaints. Many carriers offer employee incentives for meeting monthly operational goals. During the first six months of 2012, US Airways had five number ones (among legacy carriers) in the A14, bag and customer satisfaction, while Delta had 13. However, in June, the latest month available, US Airways bested Delta in A14, with 86.2% of flights on time compared to 85.5%, and had a lower rate of mishandled bags. "Competition is a good thing and Delta is a great competitor," says US Airways spokeswoman Michelle Mohr. "We're both running good operations for our customers. Operating reliability is at the core of who we are as an airline." Added Delta spokesman Morgan Durrant: "The winners here are Delta customers and the flying public at large." The four network carriers face unique challenges because they operate hubs, where on-time departures depend on good weather and perfect timing by multiple participants at various times throughout each day. Nevertheless, during the first quarter, Delta ranked third among all carriers in on-time arrivals, while US Airways tied for fifth with Southwest ( LUV), which does not operate hubs. In the second quarter, Delta ranked fourth among all carriers, while US Airways was fifth. The improvement in US Airways operations began in 2007. That March, the carrier reported an abysmally low on-time arrival rate of 55.5%, reflecting a schedule meltdown following a botched effort to move to a single reservations system after its 2005 merger with America West. By March 2008, US Airways had an on-time arrival rate of 79.1%, first among its peers, and its third number one ranking in four months.