An investigation is underway into the Delta plane that crash-landed Monday in Toronto. What caused it remains to be seen, but here's what we know so far.

One passenger said he was “drenched with jet fuel” as the planed rolled upside down and another claimed the crash occurred due to the flight crew’s "inadequate training," according to the lawsuits.

Investigators are looking into how all 76 passengers and four crew members aboard Delta Air Lines Flight 4819 survived after the plane crash-landed in Toronto on Monday.