Al-Megrahi, who has repeatedly protested his innocence, lost an appeal in 2002 and last year failed to secure his release on the grounds he was dying.
'Fight for justice'
The latest trial comes nearly two years after the Scottish Criminal Cases Review Commission referred the case for appeal, saying there were grounds to suspect that there had been a miscarriage of justice.
The former Libyan secret service agent was sentenced to life in prison for blowing up the aircraft at a special tribunal in the Netherlands in 2001.
The three Scottish judges at the tribunal said he should serve a minimum of 27 years in jail.
The aircraft, which was en route from London to New York, was blown up on December 21, 1988.
Of the 259 people on board, 189 were Americans. Another 11 people were killed on the ground.
In 2003, Libya agreed to pay about $2.7bn to families of the victims.
Last November, al-Megrahi said my "fight for justice will continue regardless of whether I am alive to witness my name being cleared".
Relatives of the victims are divided over al-Megrahi's appeal, with some believing he is innocent and others calling for him to remain in jail.
Jim Swire, whose daughter Flora was killed, told Al Jazeera on Tuesday that he did not think al-Megrahi was guilty.
"A lot of people who looked in detail at the original evidence has come to the same conclusion as I have, namely that they're pointing in a very different direction: al-Megrahi and his compatriot were not in fact guilty as charged", he said.
"He's terminally ill and probably has about a year to live. If he renounces his appeal, a prisoners' transfer agreement between Libya and Britain would allow him to return to Tripoli.
"The penalty he would pay would be no appeal and therefore his family would be, for years to come, the family of the Lockerbie bomber.
"If he hangs on here, the appeal process, scheduled to last for a year or so, might outlast his lifetime.
"It's a desperate situation for a man who always said he doesn't want to go home until he has cleared his name."