The Ukrainian military says two fighter jets have been shot down by pro-Russian separatists in the east of the country.
The rebels are also thought to have fired at the Malaysia Airlines plane which crashed last week.
The news comes as 2 military transport planes carrying the bodies of 50 victims of MH 17 disaster are en route to the Netherlands this lunchtime.
The country is marking the arrival of the bodies with a national day of mourning.
