malaysia airlines flight 370 before it vanished almost a year ago despite an extraordinary international effort. the search for mh370 has come up empty. tom foreman takes a look back at the plane's final moments. >> reporter: the mystery of flight 370 has unfolded in five terrible acts here. in the first one, it was completely unremarkable. the plane took off from coolkuala kuala lumpur supposed to be a routine flight to china where it would land around dawn. the second act occurred about 45 minutes in. that's when ground controller said they lost contact with the plane. subsequent analysis would suggest that the transponder was either turned off or stopped operating at that point. nonetheless, the plant was missing. that keyed the first search areas up toward vietnam. then came the third act.