All Nippon still does not know the exact cause of a Systems failure that hit its domestic operations on Sunday and caused the cancellation or delay of hundreds of flights.
"We have not yet been able to identify where in the connection system the trouble began," said Mineo Yamamoto, president and chief executive of ANA. "Therefore since we are not able to identify the cause we cannot give you a promise [that it won't happen again] at this point in time."
On Sunday, data flowing between ANA's host computer running its domestic reservations system and six intermediate machines began moving much slower than normal causing a data backlog that eventually clogged the system.
ANA was forced to cancel 130 flights and an additional 306 flights were delayed by more than an hour because passengers could not check-in for their flights. Around 69,300 people were affected.
In the afternoon the data began flowing again and the problem resolved itself allowing the airline to begin operating flights.
ANA also does not know what caused the system to begin working again and is working with system vendor Nihon Unisys on the problem.
The last time ANA experienced such a damaging failure in its domestic reservation system was on 21 March 2003, when the system went down for about two and a half hours early on a Friday morning of a three-day holiday weekend, and forced 150 flights to be cancelled.
"After those problems we thought we have been taking enough countermeasures to prevent another failure so it has been a great shame to see the same thing happen again on Sunday," said Yamamoto. "We will hurry to find out what happened."