RAYTHEON COMPANY 333 Notes to Consolidated Financial Statements (Continued) 33333333333333333333333333333333333333333333 Free cash flow, defined as operating cash flow less capital expenditures and capitalized expenditures for internal use soft- ware, is used by the Company to evaluate cash flow performance by the segments. Corporate free cash flow includes the differ- ence between amounts charged to the segments for interest and taxes on an intercompany basis and the amounts actually paid by the Company. The country of destination was used to attribute sales to either United States or Outside United States. Sales to major customers in 2003, 2002, and 2001 were: U.S. government, including foreign military sales, $13,436 million, $12,255 million, and $11,161 million, respectively, and U.S. Department of Defense, $11,766 million, $10,406 million, and $9,512 million, respectively. Capital Expenditures Depreciation and Amortization Operations by Geographic Areas Identifiable Assets (In millions)  2003 2002 2001 Integrated Defense Systems $6 7 $7 1 $8 Intelligence and Information Systems 25 30 45 Missile Systems 76 44 35 Network Centric Systems 55 76 67 Space and Airborne Systems 106 116 103 Technical Services 12 20 3 Aircraft 57 81 95 Other 1 — 2 Corporate 29 20 29 Total $428 $458 $461 (In millions)  2003 2002 2001 Integrated Defense Systems $5 3 $4 7 $6 Intelligence and Information Systems 29 27 65 Missile Systems 48 47 146 Network Centric Systems 62 62 121 Space and Airborne Systems 68 66 119 Technical Services 11 10 36 Aircraft 91 88 82 Other 16 12 26 Corporate 15 5 22 Total $393 $364 $677 Outside  United States (Principally  (In millions)  United States Europe) Total Sales 2003 $15,718 $2,391 $18,109 2002 14,155 2,605 16,760 2001 13,293 2,724 16,017 Long-lived assets at December 31, 2003 $ 5,381 $ 223 $ 5,604 December 31, 2002 5,391 195 5,586 (In millions)  December 31: 2003 2002 Integrated Defense Systems $ 1,657 $ 1,612 Intelligence and Information Systems 1,910 1,926 Missile Systems 4,339 4,429 Network Centric Systems 3,653 3,914 Space and Airborne Systems 3,910 3,875 Technical Services 1,399 1,372 Aircraft 2,812 3,059 Other 912 899 Corporate 3,017 2,785 Discontinued Operations 59 75 Total $23,668 $23,946