There is a separate module to handle travel expenses, you can go through these links.
http://help.sap.com/saphelp_erp60_sp/helpdata/en/b6/cd976f49e911d189060000e8322f96/content.htm
If the company is not using this module, you can use internal orders to track these expenses in FICO module.
http://help.sap.com/saap/sap_bp/BBLibrary/HTML/186_ERP605_EN_ID.htm