It's hard to specify the absolute worst because there are so many different criteria one could use, but sources such as the J.D. Power and Associates, Travel + Leisure and The Daily Beast, among others, consistently rate the following as especially dreadful temples of transportation tedium (in alphabetical order).
Boston Logan International Airport. While some airports are criticized for their lack of diversions, passengers at Boston Logan can always compete in a scavenger hunt for helpful signage. The benches there have been likened to Guantanamo Bay restraint chairs.
Chhatrapati Shivaji International Airport, Mumbai, India. One favorite pastime for passengers here is divining the odds of whether the air conditioning is going to work; the majority of flights into and out of the facility are done by mosquitoes.
Chicago O'Hare International Airport. A cold draft is great when it comes to beer; for an airport, not so much. You'll also get the cold shoulder from security staff here, who often are cited in surveys for their blank-faced, don't-ask-me style.
LaGuardia Airport, New York City. With all the charm and amenities of a bomb shelter, LGA has the distinction of being the lowest-rated airport in the United Sates by Zagat for four consecutive years (2007-2010). With a holiday on-time arrival rate of 77 percent, not only do you miss Christmas Day, but the notoriously long wait for luggage kills your New Year's Eve.
Los Angeles International Airport. The San Francisco Chronicle once referred to LAX as "eight terminals connected by a traffic jam." And after a long flight, there's nothing more comforting than running a gauntlet of unlicensed shuttle drivers trying to fill your field of vision.
Manila Ninoy Aquino International Airport, Philippines. As the facility appears to be unburdened by overly stringent rules regarding cleanliness, seasoned travelers know to bring their own Bactine, not to mention sufficient bribe money to facilitate making their connections.
Charles de Gaulle Airport, Paris. Ticket agents, security guards and the airport's own personnel evidently undergo extensive training in civility at the Don Rickles Academy. The airport's layout is said to be more confusing than a Medicare reimbursement form.
Sheremetyevo International Airport, Moscow. If you like the ambience of crowds milling about in chaotic frenzy, you'll love Sheremetyevo. Among other oddities, they keep painting the place, which has an unexpected benefit: The paint fumes mask all the cigarette smoke.
Source: Meetings & Conventions