On April 12, during a test of SOFIA’s systems involving an engine run, an anomaly occurred calling into question the flight-worthiness of Engines 1 and 4. The SOFIA maintenance team is investigating this issue. In the interim, program management has made a decision to replace the engines with spare engines. The observatory will resume flights after safety and engineering checks are completed. This down time has resulted in the estimated loss of at least eight science flights. The Cycle 5 observing schedule is being revised to recover most of the science flights later this year by exercising some built-in contingency in the observing schedule.