Are flags of non-member observer states raised at the UN Headquarters?

On 10 September 2015, the General Assembly passed A/RES/69/320, Raising the flags of non-member observer States at the United Nations, by a recorded vote of 119 in favour to 8 against (Australia, Canada, Israel, Marshall Islands, Federated States of Micronesia, Palau, Tuvalu, United States), with 45 abstentions. 

Currently, there are two non-member observer States at the UN: the Holy See and the State of Palestine.

The Holy See became a Permanent Observer State at the UN on 6 April 1964. The rights and privileges of the Holy See were expanded by the General Assembly in 2004 with the adoption of A/RES/58/314, Participation of the Holy See in the work of the United Nations.

The State of Palestine became a Permanent Observer States on 29 November 2012 with the adoption of A/RES/67/19, Status of Palestine in the United Nations. Debate on this resolution was recorded in A/67/PV.44.

The flag of the Holy See was raised by the UN for the first time on 25 September 2015, to coincide with the arrival of Pope Francis to the UN.

The Palestinian flag was raised for the first time on 30 September 2015, when Palestinian Authority President Mahmoud Abbas delivered his remarks to the General Assembly's General Debate.