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.

All 80 people aboard the Delta plane that flipped upside down and crash landed in Toronto survived, but three, including a child, are critically injured.