It's been more than a week since Malaysian Airlines flight 370 disappeared.
Authorities are digging more into the background of everyone on board.
Investigators believe someone intentionally flew the plane off course.
Authorities visited the homes of the pilot and co-pilot this weekend.
Malaysia's Prime Minister says a satellite picked up a signal from the plane seven-and-a-half hours after take off.
"It really seems that somebody took control of this aircraft and flew it for some time after the communication system were turned off," said CBS News Senior Security Analyst Michael Morell.
Investigators have seized a flight simulator from the home of the pilot.
The CEO of the airline says the co-pilot was who last spoke to air control. They say that transmission happened after the plane's transponder was shut off.
The search is now focusing on two routes stretching thousands of miles north and south. The USS Kidd and surveillance aircraft continue to search the waters for debris but have found nothing so far. Because radar would have likely picked up the plane along the northern route, US investigators believe the southern route is the more likely possibility.
Some 26 countries are involved in the search. Australia is leading efforts in the Southern Indian Ocean. Experts say if the plane went down there it will be very difficult to find.