The data showed the average forces of a soccer-ball header were similar to those exerted on the head by punches from amateur boxers, according to Daniel Plant, a researcher in Imperial's department of mechanical engineering, who presented the data Friday at a helmet-safety science conference at the university.

WSJ: Soccer 'Header' Impact Likened to Hard Punch

Some safety experts are concerned, but not alarmed, about the mechanical setbacks with the Dreamliner since its delivery to airlines beginning in 2011, following years of manufacturing delays and cost overruns.

CNN: Airline: Dreamliner fuel leak due to an open valve

Jordan also repeated his belief that the plane had no safety problems, saying the company would have voluntarily grounded it if any mechanical trouble had been found.

CNN: Deadly Florida crash site a logistical puzzle