EMERGENCY 7 passengers complained of headaches on board United Airlines #UA1218

A plane of United Airlines was forced to turn around and land on Chicago International Airport after a technical problem with the pressurization system, few minutes after takeoff.

The aircraft, a Boeing 737-900 flight UA1218 , which was to make the connection between Chicago O’Hare International Airport and Denver International Airport (Colorado) with 174 passengers and 7 crew members on board, departed to 8:40 am local time and was flying a few minutes when the pilots were alerted to a technical problem on the pressurization system. 
Moments later, seven passengers complained of nausea and headaches. The pilots then turned around and asked the presence of medical services upon arrival.

The plane landed at 9:50 am without incident and sick passengers were transferred to medical vehicles.