Why weren’t Su-35s vectored to intercept the drones?
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They were busy showing off their flying skills and plane maneuverability at an airshow.
Here's a video of the "Cobra" maneuver. Very impressive.
https://www.youtube.com/shorts/mZFr55IjHeE
The ruzzians claim the maneuver can defeat a missile attack.
Here's the limitations:
The maneuver would have to be perfectly timed.
The maneuver can only be performed at low altitude and at low airspeed.
The maneuver won't defeat a heat seeking missile.
The ruzzians had better find a way to shoot down the long range Ukrainian drones or 2024 will be a bad year for their industry, infrastructure, and revenue.
IMHO, SUUs and MiGs would be their best option.