What factors affect boundary layer transition from laminar to turbulent?

Boundary layer transition depends on: Reynolds number (higher Re promotes transition), pressure gradient (adverse gradients trigger transition earlier), surface roughness (trips transition), freestream turbulence (higher intensity causes earlier transition), surface temperature gradients, and acoustic disturbances. Transition can be predicted using methods like the e^n method (n typically 9-11 for flight conditions) or stability analysis. Understanding transition is crucial for drag prediction and designing natural laminar flow (NLF) surfaces.