A Skywest Airlines plane landed Tuesday at General Mitchell International Airport in Milwaukee after the cockpit crew reported that only two of the three sets of landing gear would lower. All 36 passengers and three crew members aboard the Bombardier CRJ200 deplaned safely.
Last Saturday, Delta Connection Flight 4951, operated by Atlantic Southeast Airlines, made an emergency landing at John F. Kennedy International Airport because of a problem with its landing gear. There were no injuries in that incident, which involved a CRJ-900 twin-engine jetliner.
An NTSB spokesman tells CBS News that the Board is specifically investigating whether there are "commonalities" among the recent accidents involving Bombardier aircraft and not fully deployed landing gears.
NTSB Spokesman Keith Holloway says that while the Board has "not initiated any special investigation per se" into Bombardier landing gears and, "at this point, we have not made any connections between the two accidents."
In addition to the latest incidents, Federal Aviation Administration documents reveal at least three other landing gear problems with Bombardier jets since 2008.
Bombardier spokesman Marc Duchesne did not immediately comment on the latest problem in Milwaukee, but said Tuesday that there are no issues with the landing gear on the CRJ series planes.
"These aircraft are in service with more than 60 airlines over the world," he said. "The aircraft has logged more than 27 million flight hours and more than 22 million takeoff and landing cycles, so these are very good and reliable aircraft."
Aviation experts note that while a plane landing without its full gear can be harrowing for those on board, usually such landings result in few injuries or fatalities.
"It creates a lot of sparks and damages the airliner to some extent," said Doug Moss, a pilot who runs AeroPacific Consulting in Torrance, California. "The general rule is no one gets hurt and they are fairly infrequent."
A CBS News search of the NTSB database shows that, including last night's emergency landing, Bombardier planes have been involved in a total of seven incidents since June 2005 in which an emergency landing was made with a landing gear being only partially extended or not extended at all. Six of the incidents have occurred in just the last two years.
Prior Bombardier landing gear landing gear emergencies since late 2008 include:
On Dec. 15, 2008, a Mesa Airlines CRJ-900 landed safely at Chicago O'Hare Airport after the crew noticed an indicator light showing trouble with the landing gear.
On June 11, 2009, an Atlantic Southeast Airlines CRJ-200 couldn't extend its left landing gear but landed safely in Atlanta's Hartsfield Airport.
On May 23, 2010, a Skywest Airlines CRJ-200 couldn't extend its nose landing gear but landed safely at an Ontario, California, airport.
The New York Daily News reported that in April a "gear disagree" message appeared on a South Africa Express CRJ-200 flight approaching Windhoek Airport in Namibia.
Airline safety consultant Keith Mackey said regional jets, because they fly more frequently, may encounter landing gear problems more often.
"A Boeing 747 typically flies longer-distance flights, but some of these (regional) planes can do 30 landings a day," he said. "Each time you cycle the landing gear, the probability goes up."
A CBS News search of FAA records shows that the following U.S.-based airlines fly Bombardier aircraft. Noted below are the number of Bombardier planes each of the airlines have and which major carriers each regional airline serves as a feeder for:
Air Wisconsin (United Express) - 70
American Eagle - 33
Atlantic Coast (United Express) - 1
Atlantic Southeast (Delta Connection) - 164
Comair (Delta Connection) - 96
Express Airlines (Northwest Airlink) - 142
Horizon Air - 13
Mesa Airlines (America West, US Airways Express) - 72
Mesaba (Northwest Airlink) - 60
PSA (US Airways Express) - 49
Skywest (Delta Connection, United Express) - 244