The U.K. Cabinet Office says several major defense programs are in danger of being unachievable or may need to be rescoped in order to stay on track.

In its annual report, published May 24, the Major Projects Authority (MPA) gave the Watchkeeper tactical UAV and Queen Elizabeth II-class aircraft carrier programs red traffic light ratings, indicating a low level of confidence in the delivery of the program. The authority uses a traffic light system to rate the risk of each program’s delivery, with those “red” or “amber/red” deemed potentially unachievable.

The £1.08 billion ($1.6 billion) Watchkeeper program, led by Thales UK, should have delivered the first UAV to the British army for operations in 2012, but the system was not given its release to service. In its report, the MPA says Watchkeeper is “particularly challenging” because the aircraft is the first of its size to be operated in the U.K. under a “reinvigorated regulatory process,” indicating the role of the Military Aviation Authority in the aircraft’s certification.

“The milestones in support of ISD [in service date] are being re-profiled to provide a robust cost forecast of the revised Watchkeeper schedule,” the report states.

The report says work on the aircraft carrier program was being “re-baselined” following the 2012 decision to go back to the short takeoff and vertical landing variant of the F-35. The report says that sea trials for the first vessel will begin in 2017, and flying trials with the F-35 in 2018.

Meanwhile, the Project Julius program to harmonize the fleet of Chinook helicopters with a standard cockpit and engine system was given an amber grading, as was the Puma helicopter life extension program and the introduction of the AgustaWestland AW159 Wildcat.

The report notes that the navy Wildcat’s primary weapon, the Future Anti-Surface Guided Weapon (FASGW) Heavy program in conjunction with France, has been “decoupled” to prevent delays on the aircraft getting to its interim operating capability. Work is now ongoing to advance the introduction of the Thales-developed FASGW Light weapon in a bid to address the shortfall, while the introduction into service of the army Wildcat has slipped from January 2014 to August 2014.

Of the 191 spending programs being monitored by the MPA, worth £350 billion, the defense ministry’s share is the largest, valued at some £88 billion. The vast majority of defense programs are in the amber or green categories, according to the MPA.