"ArduPilot can handle tasks like stabilizing a drone in the air while the pilot focuses on moving to their next objective. Pilots can switch them into loitering mode, for example, if they need to step away or perform another task, and it has failsafe modes that keep a drone aloft if signal is lost."
Not for this task, but could be used autonomously. If they trusted that these planes were still in the same spot, and their GPS coordinates were accurate to 10 cm, then what they could do is just program the drones to fly a preset route at preset heights, stop over the plane's wing and then descend all the way to 0 meters.
Even with that level of target knowledge (I suspect the US has the investment in the sensor-targeting links to be able to use satellites to know within cm where planes were within a five minute window, but am not sure about other nations) you'd want to have some that were available for later re-targeting to handle misses. Nuclear weapons war plans solve this by relentlessly re-targeting again and again (declassified 1960's USAF war plans called for over 70 different missiles to hit Moscow alone) but with the smaller damage radius of conventional weapons you either end up with a second strike to make sure you get all the survivors of the first strike- or have a trained human who knows the targeting priority in the loop available to update targeting on the fly.
"ArduPilot can handle tasks like stabilizing a drone in the air while the pilot focuses on moving to their next objective. Pilots can switch them into loitering mode, for example, if they need to step away or perform another task, and it has failsafe modes that keep a drone aloft if signal is lost."
So it is not fully autonomous.