According to a flight monitoring service, Flightaware, the flight left Boston at 3 a.m. local time (1.30 p.m. IST) and reached Paris at 2.46 pm local time (7.16 p.m. IST).
A passenger on the flight, Jona Kallgren, recorded a piercing loud noise that was heard, according to WCVB TV.
WHDH TV reported that a passenger on the flight suffered a "medical emergency" after it was diverted and was met on landing by medical personnel who took the passenger to a hospital.
Earlier, a Delta representative said that the aircraft was diverted to Boston because of a "mechanical issue" and another aircraft and crew were being sent there to take passengers to Paris.
Another flight monitoring service, Flightstats, said the aircraft was a Boeing 777-200 with the tail number N864DA.
According to Airfleets.Net, which has an aircraft database, that plane was 20 years old and had its first flight in 1999.
A Flightstats tracking map showed that the flight that left Las Vegas at 12.22 p.m. local time on Thursday (1.52 a.m. Friday IST) was nearing the Atlantic leg of the flight when it was turned around near the border of Quebec and Newfoundland provinces in Canada and diverted to Boston, reaching there at 9.32 p.m. (8.02 a.m. Friday).
( With inputs from IANS )