The Egyptian delegation was excluded from the Islamic foreign ministers' conference in Morocco today, an unprecedented rebuff that emphasized how Egypt has been ostracized by its traditional friends since signing the peace treaty with Israel.

Although President Anwar Sadat is defiant of his critics, the list of economic and political organizations and groupings from which Egypt has been suspended or ousted is growing. It appears that he underestimated the determination and ability of his foes to punish him.

The Foreign Ministry published this morning a statement saying Egypt had been told that a plane carrying the Egyptian delegation to the Islamic conference in the religious center of Fez would not be allowed to land. According to the Egyptians, that ban Followed a request by a Moroccan envoy that Egypt keep its delegation home "until a suitable atmosphere is created" to allow Egyptian participation.

Arab press reports and diplomatic sources indicated that not all conference participants wanted Egypt excluded, but that enough major Arab countries and Iran were threatening to boycott the meeting if Egypt participated that the Moroccans had little choice.

Major non-Arab Moslem countries such as Pakistan and Bangladesh have traditionally stayed out of inter-Arab disputes. But Asian diplomats said their sensitivities on the Jerusalem question and close ties to the oil states of the Gulf made it difficult to oppose the near-unanimous will of the Arabs.

Exclusion of Egypt from an Islamic ministerial conference is particularly galling because Egypt, seat of Al Azhar University, considers itself the world center of Islamic thought and culture. Islamic fundamentalist groups here that oppose Sadat's policies may find new political ammunition in his rejection from an Islamic gathering.

The Foreign Ministry statement said the decision by the conference against "one of the main pillars of Islam in the world can only weaken the Islamic gathering and sabotage the united Islamic path."

Up to now, most action against Egypt in the seven weeks since the treaty was signed has been economic and political. Yesterday, Prime Minister Mustafa Khalil appealed to the other Arabs to the "more reasonable" and see that the peace treaty would lead to regional stability and economic prosperity.

Sadat was less conciliatory today. Meeting with American businessmen from the Egyptian-American Business Council, set up in 1975 under President Ford, Sadat said, "You may hear, see and read about some shouts around us from the Arab world. This will never materialize into anything. It will not hinder progress either economically or politically."

Referring to Arab criticism of his previous moves, such as the disengatement agreements after the 1973 war and his trip to Jerusalem, Sadat said, "I am accustomed to this. It happened before . . . By next year this will be history."

Sadaths tactics from the beginning have been to hield nothing to his Arab critics, but to go after them with insults, scorn, attacks on their integrity and challenges to their political legitimacy. He is following the same pattern now, but this time his critics are united and this country is beginning to feel the pinch of their collective wrath.

All Cairo papers this morning printed a statement from an "official" saying there would be no commercial airline service between Egypt and Israel for 15 months.

That apparently was done to defuse persistent rumors that the airlines of all Arab countries will cancel service to Cairo the day the first flight arrives from Tel Aviv. Already there is no direct air service between Egypt and Syria, Iraq or Libya, and a complete boycott would be a heavy blow to the Egyptian economy.

All Arab countries except Oman, Sudan and Somalia have cut diplomatic ties to Egypt. They are working in regional and multinational organizations ot have Egypt excluded, with some success. A meeting of Arab and European news agencies in Vienna collapsed when the Egyptians showed up and other Arabs walked out.

Egypt has prevented transfer of the Arab league from Cairo to Tunis, blocking files, funds and personnel. But Egypt has been effectively excluded from subsidiary organizations such as the Arab Economic Unity Council.

Egypt has been suspended from the Arab Bank for Economic Development, the Arab Monetary Fund and even the Arab Postal Union, was well as agricultural, cultural and journalistic associations.

Oil has continued to flow through the Sumed piepline and the oil states have not called in their deposits in Egyptian banks. But press reports suggest that this latter move may be made soon. If so it could cut deeply into Egyptian hard-currency resources.

Sadat and Khalil have played down the potential economic impact of the Arab boycott of Egypt, but observers here believe that they may have miscalculated its extent. The observers believe it is possible that real damage could be inflicted on Egypt as boycott rules go into effect and important Egyptian exports such as films are deprived of traditional markets.