Think fast. What do you do if you are the flight deck crew of an Airbus jetliner flying from Spain to England, and while flying over France you suffer an electrical failure that takes out all of your radios, electronic instrument displays and automatic flight controls?

If you are the pilot and co-pilot of a September 2006 easyJet Airbus A319-111 flight with 144 people on board, you elect to just keep going, according to a recently released report by the UK Air Accidents Investigation Branch (AAIB), for fear that your airliner might be shot down in the post 9/11 environment.

"They were concerned that they might be intercepted by military aircraft, because of the loss of radio communications and that, given the aircraft's degraded status, they might not be able to follow an interceptor or land at another airfield," the AAIB report says. "Furthermore, they were concerned that if they deviated from the flight-planned route to divert to an en route airfield it might be considered a hostile action, which could lead to offensive measures being taken against their aircraft."

The serious incident involving the Airbus A319-111 (G-EZAC) occurred near Nantes, France on Sept. 15, 2006. The passenger flight had departed Alicante, Spain and was bound for Bristol, UK.

The aircraft had suffered a fault affecting the No 1 (left) electrical generator on the previous flight and was dispatched on the incident flight with this generator selected off and the Auxiliary Power Unit (APU) generator supplying power to the left electrical network.

While in cruise flight at Flight Level 320 with the autopilot and autothrust systems engaged, a failure of the electrical system occurred which caused numerous aircraft systems to become degraded or inoperative.

The aircraft could only be flown manually and all the aircraft's radios became inoperative and the captain's electronic flight instrument displays went blank.

In an understatement, the AAIB report said "attempts by the flight crew to reconfigure the electrical system proved ineffective and the aircraft systems remained in a significantly degraded condition for the remainder of the flight, making operation of the aircraft considerably more difficult."

The flight crew was unable to contact air traffic control for the rest of the flight, but pressed on for the aforementioned reason. The aircraft landed uneventfully at Bristol, with the radios and several other systems still inoperative.

The reasons why the electrical system could not be reconfigured by the flight crew could not be established, the AAIB stated.

The investigation identified the following causal factors in this incident:

• An intermittent fault in the No 1 Generator Control Unit, which caused the loss of the left electrical network
• An aircraft electrical system design which required manual reconfiguration of the electrical feed to the AC Essential busbar in the event of de-energization of the No 1 AC busbar, leading to the loss or degradation of multiple aircraft systems, until the electrical system is reconfigured
• The inability of the flight crew to reconfigure the electrical system, for reasons that could not be established
• Master Minimum Equipment List provisions, which allowed dispatch with a main generator inoperative without consideration of any previous history of electrical system faults on the aircraft
• Inadequate measures for identifying Generator Control Units repeatedly rejected from service due to repetition of the same intermittent fault

G-EZAC's transponder signal was lost for ten minutes, during which time the aircraft was not visible to Brest ATCC radar, leading to reduced separation with another aircraft. The loss of power to the ATC 1 transponder rendered the TCAS inoperative until the ATC 2 transponder was selected some ten minutes later. And both the cockpit voice recorder and flight data recorder malfunctioned during the power outage.

The AAIB also noted that:

The pilots were not trained in how to respond to an electrical failure involving the unrecoverable loss of the AC BUS 1, AC ESS and other associated busbars, as this was not an anticipated failure mode. Nevertheless, they were able to manage the situation and continue safely to Bristol.

The evidence shows that the loss of the AC BUS 1, AC ESS, DC ESS busbars and their dependant sub-busbars resulted in very widespread degradation or loss of multiple aircraft systems. This created an extremely demanding situation for the crew to manage. Following the failure, the commander, having lost his PFD and ND, handed over control to the co- pilot, whose displays were still available and who remained as PF. With the autopilot, flight director and autothrust unavailable, much of the co-pilot's capacity would have been absorbed with the task of manually flying the aircraft.

A serious electrical system disruption on an aircraft that is heavily reliant on electronics for most aircraft systems, such as the A320-series aircraft, will inevitably have serious and widespread effects on many of the systems. The A320 EPGS design was considered acceptable because, in the event of loss of the AC ESS busbar, most of the affected systems would be restored by manually selecting the alternate feed, which Airbus considered would typically take around one minute. In-service experience has shown that on some occasions the changeover may take longer, or not be achieved at all, as in G-EZAC's case. In this case the aircraft was stable in the cruise in VMC conditions but the failure could equally have occurred in IMC conditions and at low level in a critical phase of flight, such as the approach to land. As TCAS operation was compromised, such a failure in congested airspace might also lead to an increased risk of collision with another aircraft. With the EGPWS also inoperative, there would be no warning of the risk of collision with terrain.

Other significant systems were affected, such as the cabin pressurization system, where the automatic control function was no longer available. In this incident it did not cause the flight crew any difficulty, however had this failure occurred in other circumstances, the cabin altitude could increase excessively, requiring corrective action. The flight crew would then have to control the cabin pressure manually. Whilst the excessive cabin altitude warning would still operate, it would not be possible to deploy the passenger oxygen masks.

The AAIB investigation resulted in ten recommendations:

It is recommended that the EASA require modification of Airbus A320-series aircraft to provide automatic changeover of the electrical power feed to the AC Essential busbar in the event of de-energization of the AC BUS 1 busbar. (Safety Recommendation 2008-81)

It is recommended that the EASA and the FAA introduce certification requirements aimed at ensuring that flight deck control selectors are designed such that an immediate and unmistakable indication of the selected position is always provided to the flight crew. (Safety Recommendation 2008-83)

It is recommended that the EASA requires the modification of affected Airbus A320-series aircraft so that the loss of a single busbar does not result in the complete loss of Radio Telephony communications. (Safety Recommendation 2008-84)

It is recommended that the EASA and the FAA re-categorize the loss of all Radio Telephony communications for public transport aircraft as 'Hazardous'. (Safety Recommendation 2008-85)

It is recommended that the EASA require Airbus to review the A320-series Master Minimum Equipment List (MMEL) for the validity of dispatch with an IDG inoperative, given that an intermittent fault in a Generator Control Unit can result in significant disruption of aircraft systems. (Safety Recommendation 2008-86)

It is recommended that Hamilton Sundstrand modifies its repair and overhaul procedures to ensure that a unit with an excessive service rejection rate or a recurrent fault is not repeatedly released back to service. (Safety Recommendation 2008-88)

It is recommended that the EASA and the FAA require that approved component repair organizations have procedures in place to identify units with an excessive service rejection rate or recurrent faults. (Safety Recommendation 2008-89)

It is recommended that the EASA require improvements to the fault monitoring logic of the type of Generator Control Unit (GCU) used on A320-series aircraft with the aim of preventing the monitoring system from incorrectly interpreting a fault within the GCU as an external system fault. (Safety Recommendation 2008-90)

It is recommended that the EASA extend the guidance material provided for the EASA 25-1309 certification standard for failure effect analyses, to include consideration of the effects of delayed or non-achieved crew actions, in addition to crew errors. (Safety Recommendation 2009-063)

Fast forward to Aug. 27, 2009.

An Indian Air Force MiG-29 was scrambled to intercept a Bangkok-bound Air France Airbus A343 after the airliner failed to identify itself correctly, according to Agence France Press.

The Russian-built fighter based in northern India intercepted Air France Flight 164 after it transmitted incorrect identification codes upon entering Indian airspace, the Indian AF said, adding that the Air France flight deck crew did not identify the jetliner as a "friendly" aircraft.

The aircraft was picked up by IAF radars southeast of Amritsar in the Northern Sector. The airliner was flying at an altitude of 37,000 feet and entered Indian airspace on an established border entry point on ATS route. The aircraft was not in communication and the secondary radar response 'squawk' (Identification Friendly or Foe code) was not correct and the aircraft was identified as 'Unknown'.

It was only later that the Air France airliner started transmitting correct secondary radar response code and was picked up and identified by air defense radar as an A-343 operating as Air France Flight 164.