Like that new-plane smell? It'll be a while for new Delta

Combined, Delta Air Lines and Northwest Airlines would have a mammoth, 1,000-plus aircraft fleet with which executives could deliver on the promise of a single U.S. carrier capable of connecting the world.

But those 1,097 aircraft could also be a mammoth headache to manage.

Between them, Delta and Northwest fly more than a dozen models of airplanes, with only the Boeing 757 and the regional jet CRJ-200 in common. The aircraft potpourri -- Airbuses, Boeings, old McDonnell-Douglases and new Embraers -- runs counter to the streamlined fleet many experts contend is necessary to keep maintenance issues to a minimum and the greatest number of planes in the air instead of the hangar.

"The fleets don't fit together well at all," said Ernie Arvai, an aviation consultant with the Arvai Group. "There is really no synergy. It's incompatibility multiplied." Each make of aircraft requires its own aircrew training, spare parts, maintenance training and manuals.

Delta CEO Richard Anderson this week argued that the diversity of aircraft is a strength, not a weakness.

"The fleet integration actually works out quite well because we don't have common fleet types. ... We don't have to sit down and merge a lot of maintenance programs," Anderson told Wall Street analysts.

"That's the first time I've heard that rationale," said Scott Hamilton, a Seattle-based aviation industry consultant with the Leeham Co. "I thought that's what consolidation is all about."

But passengers eager to see something other than an aged Northwest DC-9 or a legacy Delta MD-88 pull up to the gate for their next flights might have to wait for some time. The two principal manufacturers used by Delta and Northwest -- Boeing and Airbus -- are booked with orders for several years. There's a four- to five-year backlog for the Boeing 777, a wide-body fairly new to the Delta fleet, Hamilton said. Airbus is back-ordered until 2012.

Northwest is scheduled to be the first U.S. carrier to get the widely anticipated Boeing 787 Dreamliner, but Boeing repeatedly has pushed back the delivery time, now into 2009.

"For the short term, they have to fly with what they have," Hamilton said.

By most accounts, Northwest flies the oldest fleet among major U.S. carriers, pulled down by its nearly 100 DC-9s, which have an average age of 35.6 years.

Airsafe.com calculated that the overall average age of the Northwest fleet, including some of its newly acquired Airbuses, is 18.5 years. Delta's fleet is somewhat younger, averaging 13.8 years, according to the same report.

Both airlines have planes on order, although not enough for a wholesale reconfiguration of their fleets. In addition to 18 Boeing 787s, Northwest has seven mid-size A320s and A319s on order. Delta has 50 orders for the newest generation of 737s and eight orders for the 777. Given those orders, it appears that the new Delta, a Boeing mainstay, will remain a customer of Airbus as well.

But there are ways to take advantage of the existing mismatched fleets, analysts said.

Where the airlines currently compete with hub-to-hub service, two smaller planes can be replaced with one larger one. For example, a 180-seat 757 could replace a 148-seat A320 and fly at capacity, producing more revenue.

"They can better fit the airplane to the route," said Dan Kasper, a transportation analyst for LECG, a Massachusetts-based economic and financial consulting firm. "There are potential for synergies where they can shift up to a larger aircraft."

Northwest spokesman Tammy Lee said that Delta has more planes suitable for smaller markets while Northwest has the largest planes for heavy international travel. Northwest also has more mid-size planes in the 77- to 125-seat range.

"We think the benefits of the proposed merger will be more than advertised -- and without a lot of pain," McAdoo wrote.

David Phelps • 612-673-7269