Arnarson and Pordarson didn't deploy their main parachutes, which could mean that they lost altitude awareness and didn't know where they were during the jump, Skydive City co-owner T.K. Hayes has told The Associated Press. Both victims had backup automatic activation devices, but they didn't have time to fully inflate.
Out of just over 3 million jumps, 19 skydivers died last year across the U.S., according to the United States Parachute Association. Experts said it is "very rare" for two jumpers to die in the same accident.
The victims were part of a skydiving group from Iceland who travel to Florida annually.