Although actual airplane crashes are rare, the rate of near collisions on airport runways is increasing and experts predict a record number of near collisions on runways this year.

Near collisions are incidents when an aircraft, vehicle or person is on a crash course with an airplane that is landing, taxiing or taking off.

• Through September, there were 234 such incidents this year -- compared with 209 for a similar period last year.

• There were a record 289 close calls last year.

• In 1988, there were 0.30 reported incidents per 100,000 take-offs and landings -- a figure that rose to 0.47 last year.

Since 1990, the National Transportation Safety Board has been calling for a high-tech system that would warn pilots of imminent ground crashes. The Federal Aviation Administration originally estimated it could install such a system -- called the Airport Movement Area Safety System -- at 34 of the nation's busiest airports by 1996.

But work on it is four years behind schedule and the FAA now says it will take until March 2000 to complete -- at an estimated cost of $74.1 million. Air traffic controllers say the warning system has been plagued by too many false warnings that cause them to question whether it is flagging a real emergency or just making noise.

More than 600 million passengers boarded commercial planes last year -- a figure expected to rise to 800 million by 2007.