An amphibious aircraft without airstairs which comprises: a fuselage, one or more airfoils, one or more empennages, a plurality of engines (14, 30), a plurality of undercarriages (4, 9) and a plurality of propeller devices, wherein: the fuselage is flat and oblong shaped and comprises a passenger cabin, a pilot compartment and a cargo hold; the pilot compartment protrudes from the fuselage and the passenger cabin and cargo hold are located at the same floor in the aircraft; a cross-sectional shape of the fuselage resembles a cross-sectional shape of the one or more airfoils; the one or more airfoils extend to two sides from a top central part of the fuselage; a jet engine of the one or more engines (14, 30) is mounted on the rear of the fuselage near an empennage of the one or more empennages; all of the undercarriages are mounted in the fuselage; two front undercarriage bays and several main landing gear bays are mounted in the passenger cabin of the fuselage; front undercarriages of the one or more undercarriages are mounted within the front undercarriage bays; main landing gears are mounted within the main landing gear bays; all of the front undercarriages and the main landing gears are vertically retractable; all of the front undercarriage bays and the main landing gear bays are mounted with front and rear sliding doors; each of the propeller devices comprises a fuel-oil engine of the plurality of engines (14, 30), a stationary gearbox, a moveable gearbox, and a propeller; the propeller devices are located in a propeller chamber at each of the two rear corners of the fuselage inside the cargo hold; each propeller chamber is mounted with front and rear sliding doors which in use, when the aircraft functions as a floatplane on water, slide forward to open a lower opening of the propeller chamber; and each moveable gearbox and propeller are extendable through the lower opening of the propeller chamber into the water. a fuselage, one or more airfoils, one or more empennages, a plurality of engines (14, 30), a plurality of undercarriages (4, 9) and a plurality of propeller devices, wherein: the fuselage is flat and oblong shaped and comprises a passenger cabin, a pilot compartment and a cargo hold; the pilot compartment protrudes from the fuselage and the passenger cabin and cargo hold are located at the same floor in the aircraft; a cross-sectional shape of the fuselage resembles a cross-sectional shape of the one or more airfoils; the one or more airfoils extend to two sides from a top central part of the fuselage; a jet engine of the one or more engines (14, 30) is mounted on the rear of the fuselage near an empennage of the one or more empennages; all of the undercarriages are mounted in the fuselage; two front undercarriage bays and several main landing gear bays are mounted in the passenger cabin of the fuselage; front undercarriages of the one or more undercarriages are mounted within the front undercarriage bays; main landing gears are mounted within the main landing gear bays; all of the front undercarriages and the main landing gears are vertically retractable; all of the front undercarriage bays and the main landing gear bays are mounted with front and rear sliding doors; each of the propeller devices comprises a fuel-oil engine of the plurality of engines (14, 30), a stationary gearbox, a moveable gearbox, and a propeller; the propeller devices are located in a propeller chamber at each of the two rear corners of the fuselage inside the cargo hold; each propeller chamber is mounted with front and rear sliding doors which in use, when the aircraft functions as a floatplane on water, slide forward to open a lower opening of the propeller chamber; and each moveable gearbox and propeller are extendable through the lower opening of the propeller chamber into the water. the fuselage is flat and oblong shaped and comprises a passenger cabin, a pilot compartment and a cargo hold; the pilot compartment protrudes from the fuselage and the passenger cabin and cargo hold are located at the same floor in the aircraft; a cross-sectional shape of the fuselage resembles a cross-sectional shape of the one or more airfoils; the one or more airfoils extend to two sides from a top central part of the fuselage; a jet engine of the one or more engines (14, 30) is mounted on the rear of the fuselage near an empennage of the one or more empennages; all of the undercarriages are mounted in the fuselage; two front undercarriage bays and several main landing gear bays are mounted in the passenger cabin of the fuselage; front undercarriages of the one or more undercarriages are mounted within the front undercarriage bays; main landing gears are mounted within the main landing gear bays; all of the front undercarriages and the main landing gears are vertically retractable; all of the front undercarriage bays and the main landing gear bays are mounted with front and rear sliding doors; each of the propeller devices comprises a fuel-oil engine of the plurality of engines (14, 30), a stationary gearbox, a moveable gearbox, and a propeller; the propeller devices are located in a propeller chamber at each of the two rear corners of the fuselage inside the cargo hold; each propeller chamber is mounted with front and rear sliding doors which in use, when the aircraft functions as a floatplane on water, slide forward to open a lower opening of the propeller chamber; and each moveable gearbox and propeller are extendable through the lower opening of the propeller chamber into the water.