The aviation sector contributes to environmental problems like climate change, resource depletion, and air pollution. We perform a systematic literature review of life cycle assessment studies to map the environmental impacts in the sector and provide methodological recommendations. The sector is divided into cross-cutting systems, namely aircraft, fuel and propulsion systems, and airports. Our review results confirm the sector's focus on climate change impacts. The mitigation strategies rely mostly on reducing CO₂ emissions during aircraft operations, like implementing sustainable aviation fuels and prospective technologies or decreasing aircraft weight with lightweight components. We use review analyses to identify and discuss knowledge gaps, such as the assessment of noise impacts or non-CO₂ flight emissions. Finally, aviation-specific recommendations are provided to LCA practitioners and aviation stakeholders with respect to data transparency and harmonization of results. Research needs, such as the development of characterization factors, are recommended to developers of life cycle impact assessment methods.