CHICAGO – Heightened security at Chicago’s two main airports could stay in place through the week and cause headaches during the busy Independence Day holiday, officials said Sunday.

“Just to be on the safe side, it makes sense, particularly on this busy Fourth of July holiday weekend, to plan ahead and allow extra time at the airport,” said Wendy Abrams, a spokeswoman for the city’s department of aviation.

Amid terrorism fears in the United Kingdom, federal officials advised the city’s Department of Aviation to boost security at O’Hare International Airport and Midway Airport until further notice.

The extra measures include random inspections of vehicles as well as increased canine units and uniformed and plain-clothed officers inside and outside of terminals.

“These will be visible security enhancements that travelers will likely notice immediately upon arrival at the airports,” Abrams said.

On Sunday, the police and fire department temporarily cordoned off an area behind O’Hare’s Lufthansa terminal after airport staff discovered a 55-gallon drum in the area. Police removed the drum without incident and found nothing harmful.

Passengers should arrive at least two hours before their flights are scheduled to depart, Abrams said.

She said authorities are working to ensure the extra security don’t slow passengers at Midway and O’Hare, which could see record numbers of passengers during the upcoming holiday.

About 254,000 passengers are expected at O’Hare Thursday, the busiest day this week. Midway’s busiest day will likely be Friday when 77,000 passengers are expected at the airport.