Passengers were allegedly told to cover their nostrils with their hands as a plane filled with smoke before being forced to make an emergency landing.
Families on board the Vueling plane from Malaga to Barcelona claim no safety masks were handed out as smoke was seen about 20 minutes before the aircraft touched down.
Dramatic footage appears to show the moment the cabin became smoky.
Video also captured travellers of all ages sliding down the chutes in an emergency evacuation after landing.
At one stage, a spokesman for 40 passengers claimed, they were told to "cover your nostrils with your hands and lower your head to your legs."
"Several people suffered panic attacks, especially when the plane had landed, emergency ramps were not activated and there was a high concentration of smoke in the cabin which made it difficult to breathe," Javier Calderón told Spanish newspaper El Pais.
The passengers have criticised the way the evacuation was dealt with and say they received better help from two Ryanair staff who just happened to be travelling on the flight.
The Vueling Airbus A320-200N was said to have been about 20 minutes from landing when smoke started to fill the cabin.
An investigation is underway but it is thought to have been caused by some plastic which combusted.
The plane landed safely at Barcelona with priority clearance before the emergency evacuation was ordered.
Dramatic footage taken by one of the passengers and posted on Youtube shows people shouting "be calm" whilst still in their seats and the smoke is clearly visible.
Men, women and children are then seen sliding down the chutes one at a time onto the tarmac just after midnight.
Javier Calderón said passengers weren't told what was going on and claimed they were very nervous.
He said the situation was made worse because there was a delay in using the front chute which was being lifted by strong winds until extra personnel were brought in to hold it down.
He said other passengers helped in the evacuation.
A child is also heard crying as passengers run to safety.
Vueling says: "Vueling is investigating the incident with the competent authorities to determine the causes.
"All customers were evacuated safely."
