Hussein's motorcade came under fire on 1 September for the second time in three months, triggering clashes between the army and the fedayeen in Amman up until 6 September. On 6 September, three planes were hijacked by the PFLP: SwissAir and TWA jets that landed at Azraq, Jordan, and a Pan Am jet that was flown to Cairo and immediately blown up after passengers were deplaned.
The two jets that landed in Jordan had 310 passengers; the PFLP threatened to blow them up if fedayeen from European and Israeli prisons were not released. On 9 September, a third plane was hijacked to Jordan: a BOAC flight from Bahrain with 115 passengers was diverted to Zarqa. The PFLP announced that the hijackings were intended "to bring special attention to the Palestinian problem".
After 371 hostages were removed, the planes were dramatically blown up in front of international press on 12 September. However, 54 hostages were kept by the organization for around two weeks. Arab regimes and Arafat were not pleased with the hijackings; the latter considered them to have caused more harm to the Palestinian issue. But Arafat could not dissociate himself from the hijackings, again because of Arab public opinion.
Source:
https://en.wikipedia.org/wiki/Black_September#Black_September