Rail cars pull the container ship Ayxo Maersk through the locks as the sun sets over the Panama Canal on March 28, 2007. Between 35 and 40 ships pass through the canal each day.
Since China joined the World Trade Organization in 2001, transit slots in the canal have become so in demand that some of the daily slots are auctioned to the highest bidder. Ships often have to wait for hours for their turn to cross the bustling waterway.
In addition to letting today's larger ships through, the expansion project is expected to relieve traffic congestion on the canal.