On January 20, 1933, the aircraft was moved to E.M. Laird workshops at 5321 W. 65th St. in the Clearing Industrial District, Chicago, where she was rebuilt and made suitable for the transatlantic flight. New elongated wings were built, with two additional gasoline tanks installed in the fuselage, having 220 and 185 US gallon capacity, each equipped with emergency dump valves. Beneath the pilot's seat a 25 US gallon oil tank was outfitted with 12 cooling tubes. A longer horizontal stabilizer was built. Aero-dynamic wheel pants were installed, and the fuselage received a new fabric covering. A new, higher compression engine, 365 hp (272 kW) Wright Whirlwind J6-9E, ser. No. 12733, had a "speed ring". On March 29, 1933, the rebuild was complete, and the registration number was changed to NR-688E, and the aircraft was painted orange. On both sides of the fuselage scrolls with the names of the sponsors were painted. The aircraft was dubbed "Lituanica" (Lithuania in Latin).
Darius and Girėnas were Lithuanian pilots, emigrants to the United States, who made a significant flight in the history of world aviation. On July 15, 1933, they flew across the Atlantic Ocean, covering a distance of 3,984 miles (6,411 kilometers) without landing, in 37 hours and 11 minutes. In terms of comparison, as far as the distance of non-stop flights was concerned, their result ranked second only to that of Russell Boardman and John Polando, and ranked fourth in terms of duration of flight at the time. Although Darius and Girenas did not have navigational equipment and flew under unfavorable weather conditions, the flight was one of the most precise in aviation history. It equaled, and in some aspects surpassed, Charles Lindbergh's classic flight. Lituanica also carried the first Transtlantic air mail consignment in history.
Even today an ordinary, unprepared plane of this size cannot cover such a distance (Cessna 152, for instance, can fly only 1200 km). The flight was also important from the scientific point of view, exploring the air flows and possibilities of this type of the aircraft. They were the first who officially carried air mail from North America to Europe.
In their last letter, the pilots wrote that either a successful flight or a possible catastrophe would be valuable and significant enough and hence it is worthwhile to fly in either case.
After taking off from Floyd Bennett Field in New York on July 15, 1933, 6:24 AM EDT, Darius and Girėnas in their Lituanica successfully crossed the Atlantic, only to perish on July 17, 0:36 AM (Berlin Time) by the village of Kuhdamm, near Soldin, Germany (now Pszczelnik, Myslibórz area, Poland).(52°51'11.57"N 14°50'17.78"E ) The planned route was: New York - Newfoundland - Atlantic Ocean - Ireland - London - Amsterdam - Swinemünde - Königsberg - Kaunas (a total of 7,186 km). Due to weather conditions over Ireland, they veered to the north and reached Germany via Scotland and the North Sea. In 37 hours and 11 minutes, until the moment of the crash, they had flown 6411 km (over 7000 km in actual flight path), only 650 km short of their goal — Kaunas.
A Lithuanian board of investigation was appointed to determine the cause. It concluded that the pilots were properly qualified, and the aircraft was properly outfitted. They added that the most difficult part of the flight was executed with great precision. The commission concluded that during the crash the aircraft engine was running (the propeller was rotating), and there was enough fuel on board (see , for instance).
Some sources mention pilot error, but both pilots were highly experienced. During his career as pilot, Darius had never been involved in any previous accidents. In 1931, Girėnas had won first prize in a flight festival in Chicago for gliding his plane and landing with a dead engine.
According to the board, the catastrophe occurred due to difficult weather conditions combined with engine defects. There were rumors and suspiscions in some quarters, that the plane was shot down, having been mistaken for a spy plane, because it flew near a concentration camp. Autopsies of pilots revealed no signs of any bullets. However, not all parts of the plane were returned to the Lithuanian government.
A few months after the Lituanica tragedy, some prominent members of the Chicago Lithuanian community discussed the possibility of financing another transatlantic flight. This idea was greeted with much enthusiasm, and enough funds were raised during the Great Depression. A faster and more modern Lockheed Vega was purchased from the Lockheed Aircraft Corp., the same model used by Wiley Post in his round-the-world flight, and by Amelia Earhart, the first woman to fly solo across the Atlantic.
The aircraft was christened Lituanica II on Sunday, April 22 1934. When the pilot originally chosen for the flight unexpectedly resigned in the spring, the Lithuanian organizers turned to Felix Waitkus, and he accepted the challenge. Although he landed in Ireland and not in Kaunas, he entered aviation history for being the sixth pilot to fly solo across the Atlantic.
In 1936 the Lithuanian government decided to build a mausoleum for Steponas Darius and Stasys Girėnas in Kaunas' old cemetery, that was destroyed after Soviet re-occupation. From then until the present day, the wreckage of Lituanica has been on display in the Vytautas the Great War Museum in Kaunas. At present the pilots' bodies rest in the Military Cemetery of Šančiai, Kaunas.