al-Muhaysini is calling for the pilots to be exchanged in a prisoner swap for Abu Mus'ab as-Suri, aka Mustafa Setmariam Nasar, the jihadist ideologue arrested in 2005 who advocates "personal jihad" over "organizational jihad."
The militant rebel group Ajnad al-Sham was on scene when the plane crashed. Here is Syrian Revolutionary Command Council (RCC) spokesman Abdulmoneim Zeineddine giving a speech at the site of the plane's landing.
There were six aboard the plane, 2 pilots and four crew. One crew member was summarily executed, it's not clear by whether "rebels", JaN, or locals, or why. Two pilots and three crew members were taken into custody. One crew member may have gotten away. Here's a portion of the photo showing the killing of one crew member. (I cropped it to just show the shooter, not the person being killed.)
The media's first reports of the crash used the words "rebels" to describe Ajnad al-Sham and JaN. JaN is not a "rebel" group, it's part of al Qaida and equally as violent as ISIS, although it claims not to behead people in public.
The plane was a Mi-14 ASW (Anti-Submarine Warfare) helicopter. Its tail number is visible (in Arabic.)
So what happens to the pilots and crew? Would Syria do a prisoner exchange? Is Musab al Suri still alive (it's been 10 years since his arrest)? Ajnad al-Sham and JaN say these are the helicopters used to drop barrel bombs. I doubt they'd let them live if Syria doesn't agree to negotiate.