Hundreds of people gathered at Sknyliv airfield in western Ukraine, to remember the 83 people killed during an air show Saturday.
Ukrainians are observing their second day of mourning and some families have begun burying their loved ones. Hundreds of people brought flowers and lit candles at the airfield to honor those killed and injured in the disaster.
Investigators are trying to figure out what made the plane crash. They say they are investigating two possibilities; negligence or technical malfunction. But they say they will not have more details until later in the week.
Some aviation experts question why the planes were allowed to fly so close to spectators on the ground. Mikhail Simonov, the general designer at the Sukhoi Experimental Construction Bureau, the company that designed the type of plane that crashed in Ukraine, told Russia's Ekho Moskvy radio, that in many air shows, there is a line on the ground that pilots are not allowed to cross for the safety of spectators.
The Ukrainian prosecutor general said he is also investigating whether mechanical failure played a part in the crash.
The SU-27 fighter plane was performing complicated maneuvers when the pilots lost control of the aircraft and it crashed into spectators on the ground. The aircraft then exploded in a ball of flames, hurling debris across the airfield and the estimated 2,000 spectators gathered to watch the show.
The SU-27 fighter plane has been praised for its speed and maneuverability. But the accident is another indication of the problems facing Ukraine's cash-strapped military.
Mr. Simonov said pilots often do not have enough flight time because fuel is in such short supply. Mr. Simonov said many of the pilots often have only 30-40 hours of flight time each year, when they should have about 100 hours. The Ukraine air show disaster is being described as the world's deadliest. In 1988, 70 people died when three Italian jets slammed into each other at an air show at the U.S. Air Force base in Ramstein, Germany.
Meanwhile, Russian investigators have begun looking at the flight data recorders from an airplane that crashed during takeoff Sunday near Moscow's Sheremetyevo airport. Fourteen of the 16 people on the plane were killed, and the other two are reportedly in stable condition.