B737-300 is allowed to stray from course when the FMC dropped a waypoint.

Attributes
ACN	362840
Time
Date	199703
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : fra
State Reference	CA
Altitude	msl bound lower : 33000 msl bound upper : 33000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zoa
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	cruise other
Route In Use	enroute airway : j7
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 19000 flight time type : 2000
ASRS Report	362840
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 8000 flight time type : 1000
ASRS Report	362839
Events
Anomaly	non adherence : clearance other spatial deviation
Independent Detector	other controllera
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Flying lkv-fra direct. After passing fra, ATC advised we were 4 mi left of course (left of J7), and advised to turn right and intercept airway (J7). Evidently the FMC dumped the next waypoint (derbb). We were still within the boundaries of the airway but would have had a course deviation if we had continued on present heading. (FMC did not report the discontinuity which it generated.)

Original NASA ASRS Text

Title: B737-300 IS ALLOWED TO STRAY FROM COURSE WHEN THE FMC DROPPED A WAYPOINT.

Narrative: FLYING LKV-FRA DIRECT. AFTER PASSING FRA, ATC ADVISED WE WERE 4 MI L OF COURSE (L OF J7), AND ADVISED TO TURN R AND INTERCEPT AIRWAY (J7). EVIDENTLY THE FMC DUMPED THE NEXT WAYPOINT (DERBB). WE WERE STILL WITHIN THE BOUNDARIES OF THE AIRWAY BUT WOULD HAVE HAD A COURSE DEV IF WE HAD CONTINUED ON PRESENT HDG. (FMC DID NOT RPT THE DISCONTINUITY WHICH IT GENERATED.)

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.