Boeing developed the larger 707-320 Intercontinental series of 707s with a longer fuselage, bigger wing and higher-powered engines. With these improvements, which allowed increased fuel capacity from 15,000 gallons to more than 23,000 gallons over the 707-120 version, the 707 had truly intercontinental range of over 4,000 miles in a 141-seat (mixed class) seating configuration.