The USA likes to show that it is the boss when it comes to the Persian Gulf and the Strait of Hormuz.
In April 1988, the USA carried out Operation Praying Mantis, the United States Navy's largest engagement of surface warships since World War II.
Two Iranian oil platforms, two Iranian ships and six Iranian gunboats were destroyed.
In July 1988, the USA shot down an Iranian passenger plane.
290 passengers and crew, including 66 children, were killed.
Iran Air Flight 655 was shot down by US missiles over the Strait of Hormuz, within Iranian airspace.
The missiles came from the U.S. Navy's guided missile cruiser USS Vincennes, which was inside Iranian territorial waters.
The United States did not apologize to the Iranian government. (Iran Air Flight 655 - Wikipedia)
There appears to be a disinformation campaign aimed at linking Lockerbie/Pan Am 103 with the Vincenne's shooting down of Iran Air Flight 655.
A report for Pan Am concluded, probably correctly, that the Lockerbie bomb was targeted specifically to kill a small band of US Defence Intelligence Agents, led by Major Charles McKee, who had collected evidence a drugs ring run by a CIA unit in Lebanon. (BBC Lockerbie theories)
The Lockerbie evidence appears to point to the CIA having brought down Pan Am 103 over Lockerbie.
What about Iran?
It is believed that the CIA put the Ayatollahs into power in Iran and that the heroin trade benefited from the coming to power of the Ayatollahs. (aangirfan: The Shah of Iran was toppled by the CIA and MI6? / WAS KHOMEINI AN AGENT OF THE US AND UK GOVERNMENTS?)
Reportedly, the CIA wanted the fundamentalist Ayatollahs to prevent the spread of leftist or communist ideas; and the CIA reportedly wanted to encourage the heroin trade.
Dr John Coleman considers opium to be of prime importance in the toppling of the Shah (Conspirators’ Hierarchy: The Story of the Committee of 300 - 6).
Dr Coleman writes:
Why was the Shah deposed...? In a word, because of DRUGS.
The Shah had clamped down and virtually put an end to the immensely lucrative opium trade being conducted out of Iran by the British.
At the time that the Shah took over in Iran, there were already one million opium/heroin addicts.
This the British would not tolerate, so they sent the United States to do their dirty work for them in terms of the “special relationship” between the two countries.
When Khomeini took over the U.S. Embassy in Teheran, arms sales by the United States, which had begun with the Shah, were not discontinued...
After 1984, Khomeini’s liberal attitude toward opium had increased the number of addicts to 2 million, according to United Nations and World Health Organization statistics.
Both President Carter and his successor, Ronald Reagan, willingly and with full knowledge of what was at stake, went on supplying arms to Iran even while American hostages languished in captivity...
The arms trade with Iran was sealed at a meeting between Cyrus Vance... and Dr. Hashemi, which resulted in the U.S. Air Force beginning an immediate airlift of arms to Iran, carried on even at the height of the hostage crisis the arms came from U.S. Army stockpiles in Germany and some were even flown directly from the United States with refueling stops at the Azores.
With the advent of Khomeini... opium production skyrocketed.
By 1984 Iran’s opium production exceeded 650 metric tons of opium per annum.... Iran presently rivals the Golden Triangle in the volume of opium produced.
So, perhaps Iran was no fan of Major Charles McKee.
What about the PFLP-GC?
1. Abu Nidal reportedly worked for the CIA and Mossad.
(Abu Nidal reportedly worked for the CIA and MOSSAD...)
Reportedly, Abu Nidal may have played a part in the Lockerbie Bombing.
Abu Nidal's organisation has worked with the PFLP-GC (Popular Front for the Liberation of Palestine - general Command)
2. Reportedly Ahmed Jibril (founder and leader of the PFLP-GC) had a base near Frankfort.
Reportedly, Jibril had links to alleged drugs dealer al-Kassar, who allegedly was working with the CIA in smuggling drugs into the USA on PanAm flights.
Reportedly the maker of the Lockerbie bomb was Marwan Kreesat (Khreeshat). Bomb maker Marwan Abdel Razzack Khreesat was part of Jibril’s cell.
On 26 October 1988, Khreesat was arrested and one of his bombs seized.
Then Khreesat was mysteriously released. 
Former CIA agent Oswald Le Winter stated, "…pressure had come from Bonn… from the U.S. Embassy in Bonn… to release Khreesat." 
Reportedly, Khreesat worked for U.S. intelligence. 
Allegedly, one of Khreesat's bombs was used to bring down Pan Am flight 103 over Lockerbie.
3. Former UK Labour MP Tam Dalyell and Edinburgh law professor Robert Black have urged the Scottish and UK governments to answer reports that Abu Nidal was a US agent.
"They have long believed Abu Nidal, who died in Iraq in 2002, and his Popular Front for the Liberation of Palestine General Command were responsible for co-ordinating the bomb that blew up Pan Am flight 103 over Lockerbie on 21 December, 1988 with the loss of 270 lives."
Intelligence reports, said to have been drawn up for Saddam Hussein's security services, said Kuwaitis had asked Abu Nidal, to do work for them in Iraq.
"The reports referred to Abu Nidal's 'collusion with both the American and Kuwaiti intelligence apparatuses in co-ordination with Egyptian intelligence'." - (Was Lockerbie suspect working for US? - News)
4. "Lockerbie campaigners have urged the UK Government to press Washington over claims that a now-dead terrorist leader was an American spy.
"Former Labour MP Tam Dalyell and Edinburgh law professor Robert Black said the claims should also be investigated by prosecution authorities in Scotland."
"The claims that Abu Nidal was working for the Americans would explain some of the mysteries that surround the Lockerbie outrage, they said." - Lockerbie campaigners seek answers
5. "THE CHIEF architect of the trial which convicted Abdelbaset Ali Mohmed al-Megrahi of the Lockerbie bombing has accused two of Scotland's most senior legal figures of treating the Libyan "shabbily" by delaying his appeal...
"Robert Black, professor emeritus in Scottish law at Edinburgh University, said that Lord Advocate Elish Angiolini and the Advocate General for Scotland, Neil Davidson, were responsible for delays in the appeal process." - Lockerbie bomber treated ‘shabbily’ says professor