Airlines of India - Curious flight timings for CCU-AMD

It struck me as somewhat odd that CCU-AMD is operated by IC with an ATR, showing a total flight time of 2h 5m; yet, CCU-DEL is operated by a 737 or AB320 in 2h 20m, with a 20% shorter flight distance.

Any comments or has anybody actually flown CCUAMD?

Both are on opposite corners of india (east - north, and east - west). And while the distance can certainly be operated with an ATR I seriously doubt if "long distance" flights like that are usually operated by an ATR at all, or that IC uses 737s (which are the ancient CD / Alliance Air 737-200s) on any other than milk runs to 3 or 4 small towns at a time. IC's fleet is almost all 320s (some 319s here and there)