Can I travel outside U.S. while Green Card application is pending?

Yes, but you need Advance Parole:

• File Form I-131 (Application for Travel Document) with I-485
• Advance Parole allows re-entry while I-485 is pending
• Without Advance Parole, leaving U.S. abandons I-485
• Processing time: 3-5 months

Important: Don't travel without Advance Parole if I-485 is pending. If you have valid H-1B/L-1, you can use that to re-enter instead.