MESSENGER performed a successful Earth swingby a year after launch, on 2 August 2005, with the closest approach at 19:13 UTC at an altitude of 2,347 kilometers (1,458 statute miles) over central Mongolia. On December 12, 2005, a 524 second long burn ('Deep-Space Maneuver' or 'DSM-1') of the large thruster adjusted the trajectory for the upcoming Venus swing-by.
MESSENGER made its first flyby of Venus at 08:34 UTC on October 24, 2006 at an altitude of 2,992 kilometers (1,859 mi). A second flyby of Venus was made at 23:08 UTC on June 5, 2007 at an altitude of 338 kilometers (210 mi). On October 17, 2007, 'Deep-Space Maneuver-2' or 'DSM-2' was executed successfully, putting MESSENGER on target for its first flyby of Mercury.
MESSENGER made a flyby of Mercury on 14 January 2008 (closest approach 200 km above surface of Mercury at 19:04:39 UTC), and will make two more flybys of Mercury on October 6, 2008 and September 29, 2009, successively slowing down the spacecraft. Mercury orbit insertion will be on March 18, 2011, beginning a year-long orbital mission.
During the Earth flyby, MESSENGER imaged the Earth and Moon and used its atmospheric and surface composition spectrometer to look at the Moon. The particle and magnetic field instruments investigated the Earth's magnetosphere.
The spacecraft was originally scheduled to launch during a 12-day window that opened May 11, 2004, but on March 26, 2004, NASA announced that a later launch window starting at July 30, 2004 with a length of 15 days would be used. This significantly changed the trajectory of the mission and will delay the arrival at Mercury by two years. The original plan called for three swingby maneuvers past Venus, with Mercury orbit insertion scheduled for 2009. The new trajectory features one Earth flyby, two Venus flybys, and three Mercury flybys before orbit insertion on March 18, 2011.