Transcript for The NTSB joins Costa Rican authorities to investigate a deadly plane crash

Moving on now to that vacation horror unfolding in Costa Rica. A passenger plane crashing in that Central American country, killing ten American passengers and two pilots moments after takeoff. Tonight, the NTSB is joining the investigation, as we learn new details about the American families involved. Here's ABC's Adrienne Bankert. Reporter: Tonight, investigators from the NTSB are on their way to Costa Rica to join authorities investigating why a routine charter flight crashed, killing ten Americans and two crew onboard. Oh, my god. Reporter: That plane smashing into pieces just minutes after takeoff for the capital of San Jose on new year's eve. An American tourist saw it all from a nearby restaurant. It made a really hard left-hand turn and was totally sideways, and then nose-dived straight into the ground. Reporter: The plane operated by nature air, the largest carrier in Costa Rica. The airline has a good safety record but, had one crash last year, killing one passenger. Onboard this flight, two Costa rican pilots, American tour guidamanda Giesler and two American families. Bruce and Irene Steinberg on vacation with their three sons from Scarsdale, New York. The family shares on Facebook, "We are in utter shock and disbelief right now." Outside their home today, their babysitter, inconsolable. I don't understand what happened. Reporter: Also killed, Mitchell and Leslie Weiss and their teenage daughter and son from Tampa. You never want it to happen to somebody that you know. And they were a good, good family. Reporter: Costa Rian authorities say the pilot was experienced, but the winds in that area are so strong, especially at that altitude. That same plane was delayed in landing a day before because of those winds.

This transcript has been automatically generated and may not be 100% accurate.