On July 24, 1988, a 747 carrying 260 passengers and 15 crewmembers was speeding toward takeoff at Indira Gandhi International when a signal light warned of an engine fire. The crew decided to abort the takeoff and the aircraft overran the runway and plowed through 1,000 yards of mud before it could stop. Fortunately, everyone onboard survived, but the impact caused the main gear to collapse and tore up the underbelly. Nearly 70% of the aircraft required repair or replacement.

Consequent restoration efforts amounted to the largest aircraft-on-ground job in Boeing history, requiring more than 100 mechanics, planners, engineers and inspectors to set up shop in New Delhi and work around the clock for months. Ultimately the mission was a success, as the aircraft was completely repaired (two weeks ahead of schedule even) and took flight again without difficulty. In aviation maintenance circles, AOG situations generally are thought of as problems that prevent aircraft from flying. "AOGs happen when an aircraft is not dispatchable," explains JetBlue Airways Technical Operations Inventory Audit Manager Kenny Highlander. "We follow [US] FAA guidelines as far as the operational performance of the aircraft and work from the minimum equipment list. In some cases the aircraft can still be dispatched with items rendered operable, especially if it has a backup system. For example, we have two HF radios on our A320s."

AOG situations "are rarely caused by staffing issues," says Southwest Airlines Senior VP-Operations Greg Wells. "Normally, if not always, they are technical issues, mainly mechanical issues. When an aircraft is on the ground at a station that is not one of our normal maintenance cities where we would have parts on hand, it would be considered AOG. If we have an aircraft sitting in Boise, where we have a very small operation, and we have a mechanical issue and need a part, that would require an AOG response."

Various parts suppliers offer AOG shipping to get replacement parts to maintenance crews standing by as quickly as possible. Effective communication and logistic procedures factor significantly into a supplier's ability to acquire, transport and deliver the right parts swiftly without delay. Usually AOG part requests can be fulfilled in under 24 hr.but at double the price of what it would cost under normal conditions.


Given the thousands of commercial aircraft currently flying worldwide, it's not so surprising that AOG situations are happening continuously24 hr. a day, 365 days a year. "We handle several hundred AOG shipments every day," says Sterling Courier Aviation Division President Ed Edrington. "You never know what the next call is going to be. It might be as simple as getting a valve to a nearby airport, or it may involve putting a 777 engine on a charter and taking it to India."

JetBlue estimates it handles between three and six AOGs each morning. It's impossible to predict which parts it will need to repair or replace, but the status of flight-critical systems usually determines whether or not aircraft are ready for dispatch. "We operate off loan and borrow agreements," Highlander notes. "We loan parts to other airlines and we borrow parts from other airlines, but we don't share a spares pool at this time." The carrier has on-call maintenance in its "nonmaintenance cities" but also relies on such suppliers as United Services and Nordam for unusual situations like ground damage incidents that require heavy maintenance.

Southwest says about 10 times per month it might deal with a situation where an aircraft in need of a part is grounded for longer than 1 hr. Through its stores department and maintenance bases, it tries to act as its own AOG supplier to prevent lengthy delays. "We have ways to get something to almost every station we've got within eight hours," Wells says. "Of course, if we need a part from Boeing and their AOG group, it might take a little longer, especially if it's an engine."

Most large airlines have an AOG desk run by logistics and operations staff ready to receive and make calls about grounded aircraft that need repairs. Edrington says that handling ensuing requests takes confidence and skill. "The idea is to provide fast-on and fast-off the phone service so that people at AOG desks around the country can go on to their next challenge yet feel comfortable enough that their shipment will be handled in the most efficient way possible."

What is the part and part number? Where can it be picked up? Where is it going and who will receive it? Answers to these kinds of questions set in motion AOG logistical processes of transport and delivery that put a premium on speed and time. The clock is ticking and every minute an aircraft is grounded means it's not earning revenue. "We're not trying to determine if it was a fair price for the move," recognizes Highlander. "It's more about how much money we would lose in revenue and lose in passenger commitment if folks don't make their flight."

At A J Walter Aviation, maintaining communication with customers throughout the delivery process is vital. "We keep people advised to the status of their product every step of the way," Aviation Operations Director Andy Smith points out. "We fully monitor everything. We monitor the flights. We track and trace. We make sure it's on the flight. We make sure it's landed."


Sometimes AOG situations can be extreme. Highlander recalls an instance when JetBlue had to charter a 747 to transport an engine to the Caribbean, where a plane was grounded. "It cost the company an excess of $150,000 for the move," he says. Then there's the issue of waiting and the amount of time an aircraft is grounded, which is also costly. "We've had an aircraft with ground damage out of service for over 20 days," he adds. "We also had some foreign object damage on an E-190. It took us seven days to get a rudder out of Brazil."

Sending the wrong part also can extend ground times. Southwest has learned this the hard way, Wells admits. "Often you think you have the right part but you don't," he says. "We have different series 737s so it's easy to make a mistake with parts. The serial numbers need to match. You can't even try to get by with the wrong one, even if it fits perfectly." Such mistakes could end up doubling the time an aircraft waits on the ground. "Sometimes the best-laid plans fall apart," he acknowledges. "So instead of a three-hour AOG situation, you're facing a six-hour situation."

A J Walter has various power-by-the-hour deals in place aimed at anticipating AOG situations and projecting costs over an extended period of time. Spare parts replenishment is a key component of these kinds of arrangements. "We set up mutual agreements on what is covered on your aircraft," explains Smith. "You might phone and say 'I need a piece of avionics equipment,' and we'll say 'yes that's covered in the contract' or 'no that's not covered.' If it is, we'll ship it to you and ask that you send us the part that needs repair so we can fix it and send it back to you."

The company also offers lease packs for line replaceable units. Strategically stocking LRUs near aircraft that are supported under these deals can boost response capabilities. "An airline might ask us to supply the top 50 units it uses," Smith adds. "So we'll put them in a warehouse and bill them per month under a separate lease contract on those spares. This can help avoid serious AOG situations, especially with countries that have tight customs. A part sent to Russia could be an AOG delivery, but it might take two days to clear it."


So are certain parts more prone to break than others? Edrington says that if he knew that answer he could probably retire. "In a perfect world, an airline would have every part it would need for every aircraft at every city it flies to," he posits. "But parts simply cannot be stocked at every station because the cost would be prohibitive."

Proactive maintenance is one of the best ways to minimize AOG situations, claims Wells. "We cycle parts on and off the aircraft long before it's really necessary to do so. Most of those can be reengineered, sent back and reused. But we tend to replace parts before they reach their full lifecycle. We don't want to take them to the end and edge of failure." JetBlue pursues a similar strategy, one that's based on forward-thinking decision-making and steady compliance. "Keeping AOGs in check often depends on how you maintain your fleet and try to mitigate risk," Highlander says. "One of our goals is to maintain aircraft to the highest standard possible so that when things do happen, they're easier to recover from because we're not looking at multiple solutionswe're usually looking at a single solution." This often calls for staunch adherence to a maintenance program and the ability to manage MELs effectively.

Fleet selection also can contribute to AOG frequency, notes Highlander. "I think the chances of an AOG increase when you introduce a new airframe into the system," he adds. Last year JetBlue had to deal with a software glitch that affected a variety of systems onboard its E-190s. "We've had some issues with our Embraer aircraft that have caused delays in dispatch, but we've been working with the OEM to try to correct them."

Considering the millions of parts and miles of wiring on a typical commercial aircraft, it is unlikely that AOG services will become obsolete. After all, the AOG industry, when you include all the costs associated with parts and services, is a billion-dollar business. Time is money, and you just never know what parts will one day stop working. Edrington, who has worked the trade for nearly two decades and even earned the moniker Mr. AOG, puts it this way: "You could have a fifty-dollar valve that's keeping a several-million-dollar aircraft from flying. Money is secondary to the time relationship in getting the part from where it's at to where it's needed so that the airplane can get back up into revenue service as quickly as possible."