Explained: How a corrupted file brought US aviation to its knees

On Wednesday, thousands of flights in the United States were grounded due to what was earlier believed to be a 'technical snag' but further investigation "traced the outage to a damaged database file". As per the US Federal Aviation Administration (FAA) normal operations were being restored, however, the early morning halt affected the plans of thousands of travellers looking to travel in about 9,000 plus flights. 

Here's what happened:

Airlines across the country reported an error that caused them to ground and/or delay domestic flights due to an outage of the NOTAM (Notice to Air Missions) system.

In a tweet, on Wednesday the FAA said that their "preliminary work has traced the outage to a damaged database file."

After a while, the authority switched to a backup, however, the corrupt file was found to be present there as well.

Watch | US flights resume after FAA system outage, over 4300 flights delayed

Was it a malicious attack?

Talking to CNN, the aviation authority said that it was still trying to determine the cause; whether it was a person or a "routine entry" into the database was responsible for the corrupted file.

Was it a cyberattack?

US officials have denied reports that a cyberattack could be behind the massive outage. As per Reuters, they claim to have found no evidence of such an attack.

Also read | FAA says system restored after more than 4,300 flights grounded due to technical snag

Talking to MSNBC, Transportation Secretary Pete Buttigieg said that there was no evidence of any "nefarious" causes of the outage. However, he said that at this time it could not be completely ruled out.

What is NOTAM?

The NOTAM system keeps flight crews abreast with information about any changes to airport facilities, hazards and other essential procedures. However, on Wednesday the processing of NOTAM was reportedly "impaired".

How many flights were affected?

As per estimates by flight tracking website Flight Aware, by 7 am US Eastern time (or 12 pm GMT) at least 1,230 flights were delayed. As per the website's data, by the time the system was reset around 2 am on Thursday, more than 9,800 flights had been delayed and around 900 cancelled.

Also read | Which computer glitch led to US flights cancellations? NOTAM failure explained & Airlines' updates so far

What steps did the FAA take?

Initially, the Federal Aviation Administration said it was working to restore the NOTAM system, however, later, the authority ordered to pause of all domestic flights till 9 am.

Is this the first time such an order was announced?

As per AFP, previously such a broad command was issued during the horrendous 9/11 attacks.

(With inputs from agencies)

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