Nine separate DC10 flights in 10 days this month experienced engine-related malfunctions, prompting six unscheduled precautionary landings of the recently ungrounded wide-bodied jets.

Airline officials, showing increasing irritation at the attention focused on the incidents, describe them as routine and no cause for alarm. Similarly, a spokesman for the Federal Aviation Administration said the frequency of the problems is normal.

The FAA is trying to determine, however, whether the recent 37-day idleness of the planes following the May 23 Chicago disaster may be a factor.

While the malfunctions are routine from a safety standpoint, they nevertheless are causing some fright among passengers.

"I was terrified," said Donna Wulkan, a Washington passenger whose United Airlines DC10 from Los Angeles made an unscheduled stop in Las Vegas early Wednesday morning. She recalled a "lurch" when the pilot shut down the engine, then a scurrying by "pasty-faced" flight attendants collecting drinks in preparation for the early landing.

A United spokesman said that flight was terminated because an engine-fire warning indicator went on, prompting the pilot to activate extinguishers on the number three engine, shut it down and make a precautionary landing. No fire was discovered.

A United flight between Los Angeles and Chicago made an unscheduled landing last week because of a similar apparently false fire warning.

The other DC10 flights experienced actual engine malfunctions, although no pattern was immediately discernible, according to FAA and airline spokesmen.

Two tnational Airline DC10s made unscheduled landings on July 18 and July 19 in Los Angeles and New York because of what a spokesman called "engine malfunctions." ?

A United Airlines DC10 made an unscheduled stop last Sunday at Baltimore-Washington International Airport because of engine damage caused by a broken engine blade.

A United flight made a precautionary landing in Cleveland on July 25 when engine vibration prompted the pilot to shut down the engine.

A Continental Airlines cargo DC10 experienced a "compressor stall" in one engine four hours over the Pacific from Los Angeles. The pilot shut the engine down and landed as scheduled in Honolulu.

A Continental DC10 had to abort a takeoff after it was unable to develop full power in its number three engine at an unspecified location July 15.

A United flight bound for Chicago returned to San Francisco on July 23 with an unspecified problem in its number two engine, according to an FAA spokesman.

Spokesmen for the airlines and the FAA stressed that all multi-engine jets flying in this country are capable of flight with an engine shut down, and that such shutdowns occur many times each month on almost all types of planes.

All of the DC10s affected over the past two weeks carried General Electric CF6 engines, prompting a statement from General Electric that while the company is "not alarmed" over the problems, it is conducting investigations with the airlines to determine the causes.