On April 10, 2010, Polish President Lech Kaczynski when his plane crashed near Smolensk, Russia. The following is a list of other aircraft accident involving Presidents, compiled from the Aviation Safety Network files.
17 March 1957
A Philippine Air Force Douglas C-47 crashed near Cebu, killing Philippine President Ramon Magsaysay. (ASN Accident Description)
29 March 1959
First Prime Minister of the Central African Republic autonomous territory, Barthélemy Boganda, was killed when a French Noratlas transport plane crashed near Boukpayanga. Boganda was intended to serve as the first President of the independent C.A.R. (ASN Accident Description)
13 April 1966
President of Iraq, Abdul Salam Arif, was killed in an aircraft accident near Basrah, Iraq. (ASN Accident Description)
8 December 1967
Brazilian President Arthur da Costa e Silva surived an emergency landing at Rio de Janeiro-Santos Dumont Airport, RJ (SDU) when the undercarriage of his Presidential Vickers C.90 Viscount plane failed on landing. (ASN Accident Description)
27 April 1969
Rene Barrientos, President of Bolivia died when his helicopter crashed near Arque Village, Bolivia.
24 January 1974
The President of Togo Gnassingbé Eyadéma (1935-2005) was the sole survivor when his Togolese Air Force C-47 (5V-MAG) crashed during approach near the village of Sarakawa, northern Togo. Several high-ranking military personel died in the crash.
The C-47 was replaced by a brand new Presidential Gulfstream II jet, which crashed in December of the same year. This time President Eyadéma was not on board.
24 MAY 1981
Ecuador President Jaime Roldós Aguilera was killed when his Beechcraft 20o Super King Air plane crashed into Huairapungo Mountain, Loja Province. (ASN Accident Description)
2 August 1981
Panama’s President General Omar Torrijos was killed in an accident involving a Panama Air Force de Havilland Canada DHC-6 Twin Otter airplane near Coclecito. (ASN Accident Description)
19 October 1986
Mozambique President Samora Machel was killed when his Tupolev 134 flew into the side of a mountain near Komatipoort, South Africa. (ASN Accident Description)
7 August 1988
President of Botswana, J.K. Quett Masire, survived an attack on his Presidential BAe-125 jet. An Angolan MiG-23 foghter plane fired two missiles at the plane. One missile hit the no. 2 engine, causing it to fall off the aircraft. The co-pilot made a succesful emergency landing on a bush strip at Cutio Bie. (ASN Accident Description)
17 August 1988
Pakistani president General Muhammad Zia-ul-Haq had witnessed a tank inspection at Bahawalpur. The president and his entourage, which consisted a.o. of several senior army generals and the American Ambassador to Pakistan, were returning to Islamabad in a C-130 Hercules transport plane. The airplane crashed shortly after takeoff and caught fire. All aboard were killed. (ASN Accident Description)
6 April 1994
Rwanda’s President, Juvénal Habyarimana, and Burundian President, Cyprien Ntaryamira, were killed when their Falcon 50 corporate jet crashed after being hit by a missile while on final approach to Kigali, Rwanda. (ASN Accident Description)
27 February 2004
Macedonian president Boris Trajkovski was killed when his Beechcraft 200 Super King Air crashed near Mostar International Airport, Bosnia and Herzegovina, killing all nine on board. (ASN Accident Description)
10 April 2010
A Tupolev 154M passenger jet, operated the Polish Air Force, was destroyed when it crashed on approach to Smolensk Air Base in poor visibility. All on board were killed in the accident, including Polish President Lech Kaczynski. (ASN Accident Description)
Other Leaders in involved in aircraft accidents
4 July 1943
Władysław Sikorski, Polish Prime Minister in exile, was killed in a plane crash off Gibraltar. (ASN Accident Description)
26 January 1947
Swedish Crown Prince Gustaf Adolf was killed in an accident involving a KLM Royal Dutch Airlines Douglas C-47 at Copenhagen-Kastrup Airport, Denmark. (ASN Accident Description)
30 July 1976
Joel Rakotomalala, Prime Minister of Madagascar was killed in a helicopter accident. (ASN Accident Description)
18 January 1977
Yugoslav Prime Minister Dzemal Bijedic was killed in an accident involving a Government Learjet 25B jet near Sarajevo Airport (SJJ). (ASN Accident Description)
30 July 2005
Sudanese Vice President John Garang was killed when a Mil Mi-172 he was travelling in, crashed in the Zuria Mountains of Uganda. (ASN Accident Description)
Aviation Safety Network's News 
On 24th January 1974 the President of Togo Gnassingbé Eyadéma (1935-2005) was the sole survivor when his Togolese Air Force C-47 (5V-MAG) crashed during approach near the village of Sarakawa, northern Togo. Several high-ranking military personel died in the crash.
Later Eyadéma erected a self-aggrandizing commemoration monument at the crash-site and blamed the French government to have sabotaged his plane.
Thanks for the addition. I have added it to the list in the article.
Harro Ranter
aviation-safety.net
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What about the Polish Prime Minister helicopter crash in 2003:
http://news.google.com/newspapers?nid=1350&dat=20031205&id=sB0VAAAAIBAJ&sjid=MQQEAAAAIBAJ&pg=6670,954781
[…] Presidents and leaders involved in aircraft accidents On April 10, 2010, Polish President Lech Kaczynski when his plane crashed near Smolensk, Russia. The following is a […] […]
The Brazilian prince Pedro Luiz de Orleans e Bragança was killed on the AF447 tragedy in Atlantic Ocean on May 31th, 2009. He was the fourth in the successory line to ascend to the throne.
Link: http://ultimosegundo.ig.com.br/voo447airfrance/2009/07/07/principe+brasileiro+morto+no+acidente+com+o+voo+af+447+e+enterrado+em+valenca+7160995.html
Under “others” should be former UN secretary general Dag Hammerskjold. A great leader killed in a plane crash in 1961
It has to be mentioned that in the plane crashed near Smolensk on 10th of April 2010 not one but two presidents were killed, because apart from the Polish President Lech Kaczynski also Ryszard Kaczorowski, the President of the Polish government-in-exile was on that plane:
http://en.wikipedia.org/wiki/Ryszard_Kaczorowski
On 17 February 1959, the Turkish Airlines aircraft Vickers Viscount Type 793, registration TC-SEV, carrying Adnan Menderes and a party of government officials on a special flight from Istanbul to London Gatwick Airport crashed a few miles short of the runway, near Rusper, Sussex in heavy fog and caught fire. Nine of the 16 passengers and 5 of the 8 crew lost their lives. Menderes, sitting in the back part of the plane, survived the accident almost uninjured and was hospitalized at The London Clinic 90 minutes after receiving first aid from Margaret Bailey, a local resident who rushed to the crash site.
He was on his way to sign the London Agreements on the Cyprus issue with the British Premier Harold Macmillan and Greek Prime Minister Constantine Karamanlis, which gave the three sides the right to intervene in Cyprus in case peace is broken by any of the parties.[4]
Menderes signed the London Agreement on 19 February 1959 in the hospital. He returned home on 26 February 1959 and was welcomed by even his arch-rival İsmet İnönü and a huge crowd.
Adnan Menderes was Prime Minister of Turkey Between 1950 and 1960
The Brazilian prince Pedro Luiz de Orleans e Bragança was killed on the AF447 tragedy in Atlantic Ocean on May 31th, 2009. He was the fourth in the successory line to ascend to the throne.