No need. A Canada Goose[1] can take out an engine; a flock can take out an airliner.[2] There are many drones larger than the geese, so I would expect this to be a distinct possibility.

[1] http://en.wikipedia.org/wiki/Canada_goose [2] http://en.wikipedia.org/wiki/US_Airways_Flight_1549

> usually weighs 2.6–6.5 kg

Flock of drones is unrealistic too.

I'm fairly confident it would destroy the jet engine. The shrapnel from the drone is likely to blow the very tight tolerances between the compressor blades and the body of the jet engine, causing jams.

Yet somehow it survives ice.

Drones are not made of ice.

Ice happens to hit the engines though.