There is no direct upgrade path from Oracle9iAS Rel 1 to OracleAS 10g. Furthermore, there are no white papers or support articles which discuss upgrading Oracle9iAS Rel 1 to OracleAS 10g. This is because Oracle9iAS Rel 1 was desupported on 30th June 2004 and the first production release of OracleAS 10g - OracleAS 10g Rel 2 (10.1.2.0.0) was not in shipping until January 2005.
For Apps instances, it is well documented in metalink notes
186981.1: Oracle Application Server with Oracle E-Business Suite Release 11i FAQ
207159.1: Oracle E-Business Suite Release 11i Technology Stack Documentation Roadmap
223927.1: Statement of Direction: OracleAS Integration with Oracle E-Business Suite
and 233436.1: Installing Oracle Application Server 10g with Oracle E-Business Suite Release 11i
For non-apps instances, our approach is to upgrade first to Oracle 9iAS Release 2 and then upgrade from this version to OracleAS 10g Rel 1 which is finally upgraded to Oracle AS 10g Release 3. Here's a list of high level steps:
Task 1: Install the Oracle 9iAS Release 2
Task 2: Use the Oracle 9iAS Migration assistant to migrate Oracle HTTP Server, 9i AS containers for J2EE and webcache
Task 3: Perform any manual tasks necessary to complete the upgrade of these compoents
Task 4: Install AS 10g Release 1(9.0.4) infrastructure services
Task 5: Install the Oracle Application Server 10g (9.0.4) middle tier
Task 6: Use OracleAS Upgrade Assistant to upgrade HTTP Server, containers for J2EE and Web Cache
Task 7: Perform any manual upgrade tasks necessary to complete the upgrade of each component.
Task 8: Determine an AS 10g Release 3 (10.1.3.4) topology to install and configure
Task 9: Install and Configure 10g AS release 3 environment
Task 10: Perform any required pre-deployment tasks like configure data sources, resource adapters, http server
Task 11: Redeoply your 9i AS applications on AS 10g release 3
Task 12: Verify your redeployed applications on AS 10g release 3
Task 13: Decommission the 9i AS and AS 10g release 1Oracle Homes.
So the upgrade path will be like this:
Oracle 9i AS release 1 ----> Oracle 9i AS release 2 ----> Oracle AS 10g release 1 -----> Oracle AS 10g release 3