We have studied variability of the spectral lines of the OB star delta Ori A -the brightest component of the delta Ori triple system. Forty spectra with signal-to-noise ratios nearly 500-800 and a time resolution of four minutes were obtained. We detected variability in the HeII4686, HeI4713 and Hbeta absorption and the CIII5696 emission profiles. The amplitude of the variability is about of (0.5-1)% of the continuum intensity. The dynamical wavelet spectrum of the profile variations reveals large-scale components in the interval 25-50 km/s that move within the Vsini to Vsini band for the primary star of the system, Aa¹, with a band crossing time of 4^h-5^h. However, some of the variable features go outside the band, presumably due to either imhomogeneities in the stellar wind from .Ori Aa1 or non-radial pulsations of the weaker components of the system, Aa² or Ab. The detected variability may by cyclic with a period about of 4^h. We suggest that it is associated with non-radial pulsations of the primary in the sector mode (l,m) = (2,-2).