Ann Faulds and Nancy Primrose were inside the Clutha Vaults when there was a "loud crack and a bang" and then the sound of screaming as people struggled to escape the wreckage of the bar.
Ms Faulds, 47, said: "Nancy went up to the bar to get a drink and just as soon as she came back with the drink, I just remember a loud crack and a bang.
"The whole place seemed to have come down on top of me and I just kept thinking 'This is a bomb, and I'm alive'.
"I couldn't believe I was alive. When I looked down at the righthand side at the doors... there were people getting pulled out, and I could hear voices, people saying 'Get them out, get them out'.
"I could see bodies being pulled from the wreckage, almost as if they were being pulled from underneath the floor, as if they had sunk down. I was just thinking, one of them could be my sister, where's my sister gone? Because she was standing right beside me."
Ms Faulds, from Glasgow's Springboig area, said that as she lay trapped under some debris she heard her sister screaming for her from outside the pub.
Ms Primrose, 55, had been pulled from the wreckage and managed to get to her feet and escape the bar.
The pair had been enjoying a night out as Ms Primrose got back to health following a spinal operation, the Sun reported.
Ms Faulds said: "I could hear my sister outside screaming 'My sister's in that pub'. I was trying to shout out to her 'I'm OK, I'm alive', but obviously she couldn't hear, there was so much commotion outside."
Ms Primrose, from Dennistoun, said: "It was a great vibe in the pub and all of a sudden, bang. No fire, no smoke, no sparks, nothing.
"And then I just remember somebody pulling me out. The emergency services were there within seconds.
"There were just flashing lights everywhere. There was bodies pulling together, a line, a chain, pulling folk out, and folk shouting 'Help us', 'help this person'. The support was tremendous - absolutely tremendous."
She said she had been left "devastated" by the crash. "It certainly was not what I was expecting when I was going out with my sister," she told Daybreak.
Ms Faulds' son Gary was alerted to the accident by a telephone call from a friend of his mother's. He eventually tracked her down at a hospital.
He said: "I know it's not something funny, but you don't expect a helicopter to land on top of a pub in Glasgow.
"Once I got there I couldn't find my mum or Nancy and I scrambled about for about an hour and I couldn't find them. So I started going to the various hospitals. One of my friends had tracked them down in the Victoria. I'm grateful to have them - as you can imagine."