Left, panel 1: interferometric measurements of the CO v = 3 − 1 bandhead in NGC 2024 IRS2 for run 1 (inserts 1A–1G). From top to bottom: total flux normalised to continuum (1A); wavelength-dependent visibilities for UT 3–4, 2–4, 1–4 (1B) and for UT 2–3, 1–3, 1–2 (1C); differential phases for UT 3–4, 2–4, 1–4 (1D) and for UT 2–3, 1–3, 1–2 (1E); closure phases for UT 2–3–4, 1-3–4 triplets (1F) 1–2–4 and 1–2–3 triplets (1G). Middle, panel 2: interferometric measurements of the CO v = 4 − 2 and v = 5 − 3 bandheads in NGC 2024 IRS2 for run 3 (inserts 2A–2G). Right, panel 3: interferometric measurements of the CO v = 4 − 2 and v = 5 − 3 bandheads in NGC 2024 IRS2 for run 2 (inserts 3A–3G). From top to bottom: total flux normalised to continuum (3A); wavelength-dependent visibilities for UT 2–3, 1–3, 1–2 (3C); differential phases for UT 2–3, 1–3, 1–2 (3E); and closure phase for UT 1–2–3 (3G). For clarity, the differential phases of the first and last baselines are shifted by +10° and −10°, respectively.