Click to view full size photo at Airliners.net
Contact photographer Serdar Yorulmaz
What: Delta Airlines Boeing 767-300 en route from Chicago to Paris
Delta Airlines Boeing 767-300 en route from Paris to New York over Prestwick
Delta Airlines Boeing 767-300 en route from New York to Germany over Canada
Delta Airlines Boeing 767-300 en route from Dublin to New York (ferry flight)
Where: Atlantic
When: Feb 17th, 18th and 19, 2012
Who:
Why: While en route between Chicago and Paris, the plane’s transponder failed.
The same thing occurred on the Paris-New York flight on Feb 18;
and on the New York to Frankfurt flight on Feb 18 over Canada;
and on the Dublin to New York flight on Feb 19.

There has obviously been a problem here.

The transponder code (or “squawk code”) or altitude information is designed to help air traffic controllers to identify the aircraft and to maintain separation. The plane can fly without it, but what if the safety space is breached and there is an incident?

At least the last flight was a ferry flight, and on landing, the transponder is replaced, or whatever underlying factor that is causing this is corrected! The MEL (Minimum Equipment List) does have parameters for this.