What are the approaches to improving aircraft fuel efficiency?

Fuel efficiency improvements span multiple disciplines. Aerodynamics: Drag reduction (natural laminar flow, riblets, winglets/raked tips), Higher aspect ratio wings (within span constraints), Load alleviation for lighter wing at same span. Propulsion: Higher bypass ratio engines (LEAP, GTF), Improved component efficiencies (compressor, turbine), and Lower SFC. Structures: Composite materials (20-25% weight reduction), Advanced aluminum alloys, and Topology-optimized structures. Systems: More electric (reduced bleed extraction), Efficient ECS and hydraulics, and Lighter wiring and components. Operations: Continuous descent approaches, Optimized cruise procedures, and Real-time route optimization. Quantification: 1% drag = ~1% fuel burn, 1% weight = ~0.5% fuel burn. Technology insertion: New aircraft 15-20% better than predecessor, Derivatives 5-10% through focused improvements. Timeline: New technology development 10-15 years before service; fleet replacement cycles 20-30 years limit improvement rate.