Why no Allied landings in Japan 17-28 August 1945?

Mar 2015
US air force demonstrated their logistical capability to overfly Home Islands and return to base by March 1945.
On 15th of August, Japan announced surrender by radio. Within the same 15th of August, USA proposed that Japan should send a delegation to US occupied territories, and the delegation should fly from Japan to an airfield in US occupied Okinawa, in Japanese but marked planes, already on 17th of August.
On 16th, Japan replied by radio that they had selected the delegation - 16 men exclusive of the flight crews of Japanese planes - but that the logistic arrangements for the flight would take till 19th of August.

Hostilities had stopped on 16th of August, but US air forces did continue reconnaissance flights over Japan. Without landing.
It was only on 28th of August that US planes started to land, at Atagi airfield.

Purely logistically, USA could have landed a US plane with an US delegation at Atagi already on 17th. Or landed an US plane at Atagi and picked up Japanese delegation there.

Why was neither done until 28th?

Also, how were the communications between Japan and Soviet Union?
On 7th of August, Japan and Soviet Union were at peace, with normal diplomatic relations, a Soviet embassy in Tokyo, a Japanese embassy in Moscow, and a non-aggression pact that had not been extended but that Soviet Union confirmed was binding till 13th of April, 1946.
After Soviet attack on Japan, how long did it take to make the logistic arrangements to repatriate the Japanese embassy in Moscow to Japan and Soviet embassy in Tokyo to Soviet Union?
How were such plans affected when Japan surrendered on 15th?
Nov 2019
United States
Things were fluid initially in Japan, on August 15th there was an attempted coup by the more miltaristic wing of Japan's leadership that was defeated.
On 16 August, Japan's leaders announced that their delegates had been selected and would leave Tokyo for Manila on 19 August.46 It was now only a matter of days before the long-awaited moment of final surrender would become a reality. The Manila Conference Headed by Lt. Gen. Torashiro Kawabe, Vice-Chief of the Army General Staff, the sixteen-man Japanese delegation47 on the morn- [447] ing of 19 August boarded two white, green-crossed, disarmed Navy medium bombers and departed secretly from Kisarazu Airdrome, on the eastern shore of Tokyo Bay.48 After landing at Ie Shima, according to General MacArthur's instructions, the Japanese passengers were immediately transferred to a U. S. Army transport plane and put down on Nichols Field south of Manila at about 1800 that same day. On hand to meet the Japanese envoys as they emerged from the plane was a party of linguist officers headed by General Willoughby, General MacArthur's wartime director of intelligence. Following the necessary introductions and identifications, the Japanese were taken immediately to temporary quarters on Manila's Dewey Boulevard to await the meetings scheduled for that evening.49 Less than three hours after their arrival, the sixteen-man Japanese delegation was led by General Willoughby to the first of two conferences held that night with members of General MacArthur's staff. General MacArthur him self was not present. As the solemn procession moved from Dewey Boulevard through the battered and war-torn streets of Manila and up the broad steps of the City Hall, the stony-faced Japanese officers in their beribboned gray-green uniforms, with their peculiarly peaked caps, and with their two-handed Samurai swords dangling from their waists almost to the ground, made a grim and curious picture. Shortly after 2100, the Japanese and American representatives entered General Chamberlin's office and sat down facing each other across the long, black table of the map-covered conference room.50 The meetings continued through the night of the 19th and into the next day.51 As General Sutherland led the discussions, linguists busily scanned, translated, and photostated the various reports, maps, and charts which the Japanese had brought with them. Allied Translator and Interpreter Section personnel worked throughout the night to put General MacArthur's requirements into accurate Japanese before morning. It was a matter of vital importance that all documents be capably and correctly translated so that arrangements for surrender could be completed with a minimum of misunderstanding and a maximum of speed. The conference proceeded smoothly and all [448] major problems were resolved satisfactorily. Results of the negotiations made it advisable to modify some of the original concepts on the problem of occupation. Based upon the full co-operation of the Japanese Government and Imperial General Headquarters, the new modifications provided for gradual occupation of designated areas after the Japanese had disarmed the local troops. No direct demilitarization was to be carried out by Allied personnel; the Japanese were to control the disarmament and demobilization of their own armed forces under Allied supervision.52 General Kawabe expressed his belief that the Japanese would faithfully carry out all Allied demands, but because of the unpredictable reactions of the Japanese civilian and army elements he requested that Japan be given an additional period of preparation before the actual steps of occupation were taken. General Sutherland allowed three extra days. The target date for the initial landings was postponed from 25 August to 28 August. The arrival of the advance unit at Atsugi Airfield was scheduled for 26 August. At the close of the conference, General Kawabe was handed the documents containing the "Requirements of the Supreme Commander for the Allied Powers."53 These directives stipulated General MacArthur's requirements concerning the arrival of the first echelons of the Allied forces, the formal surrender ceremony, and the subsequent reception of the occupation forces. Also given to General Kawabe were a draft of the Imperial Proclamation by which the Emperor would accept the terms of the Potsdam Declaration and command his subjects to cease hostilities, a copy of General Order No. 1 by which Imperial General Headquarters would direct all military and naval commanders to lay down their arms and surrender their units to designated Allied commanders, and lastly the Instrument of Surrender itself which would later be signed on board an American battleship in Tokyo Bay. The Manila Conference was over. The Japanese delegation left at 1300 on 20 August and started back to Japan along the same route by which it had come. The homeward trip, however, was marred by an accident which caused a few anxious moments to the bearers of the surrender documents. The plane carrying the key emissaries had to make a forced landing on a beach near Hamamatsu, and it was not until seven hours after their scheduled time of return that the members of the mission were able to report the results of the Manila Conference to their waiting Premier.54 It now remained for Japan to prepare itself to carry out [449] the provisions of surrender and to accept a peaceful military occupation of the Homeland by Allied forces.