U.S. airlines have begun bumping more passengers this year than at any time within the past six years. That’s the conclusion from the second-quarter airline statistics released last week by the U.S. Transportation Department. U.S. airlines bumped 16,300 passengers involuntarily between April and June this year (1.12 passengers per 10,000), a rate that’s one-third higher than last year. In all, the carriers bumped (voluntarily or involuntarily) about 185,000 travelers during the second quarter this year, also up from 2005. What’s causing the problem? Airlines are selling more tickets for available seats to maximize their revenues and flying planes that are much more full than in the past -- and, along the way, they run a greater risk of “overselling” those seats.

Late flights are also a growing problem. More than 25 percent of domestic U.S. flights in June came in late (at least 15 minutes or more behind schedule), with a 72.8 percent on-time arrival rate. That percentage is down from May and down from June 2005. Gold stars go to Hawaiian Airlines (for its 94.6 percent on-time rating), followed by Aloha Airlines and SkyWest. Atlantic Southeast Airlines (which carries passengers for Delta) led the pack of late arrivers with 36.5 percent of its flights off schedule in June, followed by ATA and Mesa. (The reports found that, among America’s 23 most-delayed flights, 19 of them were operated by Delta or a Delta partner airline.)

Which airline canceled more flights than anyone else? Mesa, with 5 percent of its flights canceled in June. After that, the worst offenders were ExpressJet (a Continental carrier) and American Eagle. Frontier canceled fewer flights than any other airline (only seven canceled flights in June), followed by JetBlue and Hawaiian.

For delayed or lost bags, Atlantic Southeast posted the worst record (19.2 reports of baggage complaints for every 1,000 passengers), followed by American Eagle and Comair (another Delta carrier). The best track record with luggage belonged to Hawaiian Airlines, followed by JetBlue and Northwest.

Northwest Airlines filed court papers last week asking the carrier’s federal bankruptcy judge to block any strike by flight attendants. The airline said any work stoppage (even if it’s not a full-blown strike) could lead to “massive disruption to the public” and irreparable damage to the airline due to flight cancellations and “the loss of consumer confidence.” Unlike last year’s mechanics strike, Northwest says it cannot easily or quickly hire replacement workers to step in for any striking flight attendants.

US Airways cut the fares on its popular shuttle flights between Boston and New York/LaGuardia. Fourteen-day advance-purchase roundtrip fares will drop by 54 percent on the 16 daily roundtrips on the route.

Eos asked U.S. regulators for additional flying authority last week to begin offering six weekly flights between New York/Kennedy and Zurich starting next April. Already, Eos plans to expand its New York/Kennedy-London/Stansted service to 13 weekly flights next month, along with its first New York/Kennedy-Paris/Charles de Gaulle flights next March.

Aer Lingus will now charge 4 euros (about US$5.12) per bag for checked luggage on short flights when payment is made while buying the ticket. If passengers check bags afterwards, the fee is 8 euros. These new fees will start on flights booked after Aug. 8 for travel after Sept. 5. Ryanair, one of Aer Lingus’ competitors, already charges similar fees for checked bags.

Federal aviation officials will invest $175 million in a new baggage screening system at the airport in Atlanta. The new system is already working in the airport’s north terminal. Passengers will no longer be forced to drag their suitcases to a separate baggage screening machine; instead, they can leave their checked luggage at the airline ticket counter, before those bags are then taken by conveyor belt to the new underground screening checkpoints.